Abstract: A laser driving device that drives a semiconductor laser based on a light-emitting signal includes an expansion circuit that expands a pulse width of the light-emitting signal based on a known difference between the pulse width of the light-emitting signal and a lighting pulse width of the semiconductor laser when the semiconductor laser emits light according to the light-emitting signal, and a driver that outputs a driving signal to the semiconductor laser according to an output signal of the expansion circuit.

Abstract: Many approaches to tunable lasers use an array of DFBs, where each element of the array has a different wavelength. In some operations one element of the array is activated at a time depending on the desired wavelength. For modulated applications, an RF voltage is applied to a specific element of the DFB array, generally using an RF switch. In standard configurations, the demands on the switch are relatively difficult, generally requiring low RF insertion loss and good high frequency performance to 10 GHz. The DFB arrays are generally common cathode or common anode, depending on the type of the substrate used to fabricate the devices. Described herein is an array with a common cathode or anode configuration using a MEMS based switch that shorts the selected laser to RF ground. With this topology, preferably the off-state capacitance should be low with the MEMS switch.

Abstract: A laser device capable of preventing deterioration of a light signal and a controlling method therefor are provided.

Abstract: In a method of controlling an injection-seeded laser, a response of the laser is sampled at a plurality of different laser current values. A threshold current and a slope efficiency of the sampled response are then estimated, and a bias current and a modulation current calculated based on the estimated threshold current and a slope efficiency.

Abstract: Disclosed herein is a laser driver including a light emission controlling section configured to stop generation of a control voltage by a control voltage generating section, causing a given voltage corresponding to a magnitude of a reference current to be outputted to an input node of a first emitter follower to operate the first emitter follower for a first time period from start of a light emission time period, release stop of the generation of the control voltage by the control voltage generating section, causing the control voltage to be outputted to the input node of the first emitter follower to operate the first emitter follower until end of the light emission time period of the laser, and operate a second emitter follower to discharge electric charges accumulated in the laser for a second time period after the end of the light emission time period of the laser.

Abstract: The luminance of a laser diode is a function of laser diode drive current. The luminance is also a function of other factors, such as age and temperature. A laser projection device includes laser diodes to generate light in response to a commanded luminance, and also includes photodiodes to provide a measured luminance. The commanded luminance and measured luminance are compared, and drive currents for the laser diodes are adjusted to compensate for changes in laser diode characteristics.

Abstract: A circuit for driving a light-emitting element such as a laser diode LD has a boost circuit for boosting an input voltage to supply it to the light-emitting element, a photoreceptor such as a photodiode PD for monitoring light from the light-emitting element; and a boost control circuit for controlling a boost voltage of the boost circuit based on a monitored amount of the photoreceptor. In the method for driving a light-emitting element by boosting an input voltage to supply the voltage to the light-emitting element, light from the light-emitting element is monitored and its monitored amount is used as a basis to control a boost voltage to the light-emitting element. A control circuit may be provided to control a driving current that passes through the light-emitting element based on the monitored amount of the photoreceptor.

Abstract: A driver circuit for driving loads such as LED, OLED or LASER diode devices includes a switching converter that has a switching element and reactive elements to provide an output switching voltage by sequential switching operations of the switching element. The load is connected to the output switching voltage. A linear current driver circuit is connected in series to the load and includes an amplification element and a feedback circuit with a current control input. In order to enable the circuit to be easily used, a control unit is provided with a sensing input for a current or voltage at the linear current driver. A microcontroller executes a control program for processing the sensing input and providing both a current control output and a switching control output, set in accordance with a set current value.

Abstract: Systems and methods for controlling a thermoelectric cooler (TEC) in an optical transceiver. A TEC system includes a processor that interacts with a power supply and a TEC controller to prevent inrush current. The power supply is switched by the processor and turned on only at a particular time. The power supply has a relatively large time constant such that it ramps slowly to its full value. In the meantime, the processor and TEC controller cause the temperature to ramp to a target value by repeatedly incrementing or decrementing a target value over time and by controlling when the maximum available voltage can be applied to the TEC.

Abstract: The invention provides an optical transmitter that prevents the high frequency components in the driving signal from leaking to the external power supply in a wider frequency range. The transmitter provides a shun driving configuration with a switching transistor connected in parallel to the laser diode and a load transistor connected in serial to the parallel circuit of the switching transistor and the laser diode. The load transistor operates in the common base configuration, or the common gate configuration, by which the input impedance viewed from the laser diode becomes large, while, the output impedance viewed from the external power source becomes small. Thus, the high frequency components in the driving signal applied to the switching transistor can be suppresses to appear in the external power source.

Abstract: A semiconductor laser device comprising a laser diode with an integrated photodiode, wherein one of the components of the laser diode with the integrated photodiode is also used for heating the laser diode. A simpler design of a wavelength-controlled semiconductor laser is thus obtained.

Abstract: A laser device includes a partially reflective mirror for separating laser light into monitor light and output light, a light output monitor device for detecting the intensity of the monitor light from the partially reflective mirror, a controller for controlling the intensity of the output light from the partially reflective mirror by controlling the output of a laser light source on the basis of a detection value of the light output monitor device, and a power meter device for detecting the intensity of the output light from the partially reflective mirror during a predetermined calibration time period, wherein the controller calibrates the output of the light output monitor device on the basis of a detection value of the power meter device.

Abstract: Semiconductor lasers are driven such that high output laser beams are stably obtained without a long start up time. The light outputs of a plurality of semiconductor lasers are detected by photodetectors. The semiconductor lasers are driven by automatic power control based on comparison results between the output of the photodetectors and a set value corresponding to a target light output for the semiconductor lasers. A correction pattern that corrects the set value and/or the output of the photodetectors such that the actual light output becomes uniform is generated in advance. The set value and/or the output are varied according to the correction pattern for a predetermined period of time from initiation of drive. A single correction pattern is employed in common with respect to the plurality of semiconductor lasers.

Abstract: A projection type display apparatus is provided that is safe even when a person looks directly into a laser beam. A laser operation control unit sets the output power of at least one laser source so that intensity A (mW/mm2) of the laser beam on at least one spatial light modulation element satisfies relationship of A<686×B2 when numerical aperture B on image side of an illumination optics system is set.

Abstract: The present invention greatly reduces the likelihood that fiber fusion will occur. A laser apparatus comprises an excitation light source and an optical amplifier unit, which optically amplifies by receiving excitation light that is output from the excitation light source and that transits an optical fiber. A monitor unit monitors the power level of the excitation light transmitted from the excitation light source to the optical amplifier unit side via the optical fiber.

Abstract: Fast on-line electro-optical detection of wafer defects by illuminating with a short light pulse from a repetitively pulsed laser, a section of the wafer while it is moved across the field of view of an imaging system, and imaging the moving wafer onto a focal plane assembly, optically forming a continuous surface of photo-detectors at the focal plane of the optical imaging system. The continuously moving wafer is illuminated by a laser pulse of duration significantly shorter than the pixel dwell time, such that there is effectively no image smear during the wafer motion. The laser pulse has sufficient energy and brightness to impart the necessary illumination to each sequentially inspected field of view required for creating an image of the inspected wafer die. A novel fiber optical illumination delivery system, which is effective in reducing the effects of source coherence is described.

Abstract: A method for controlling wavelengths of a multi-path laser is provided. The method includes: obtaining a difference between an actual output wavelength and a target output wavelength of each laser (S601); obtaining a corrected control amount of a temperature controller of each laser by decoupling calculation according to the difference (S602); and determining a die temperature of each laser according to the corrected control amount of the temperature controller (S603). A system for controlling wavelengths of a multi-path laser includes a multi-path laser (10), a difference module (12), a decoupling module (14), and a temperature control module (16).

Abstract: A fiber laser processing apparatus controls a LD drive current ILD in a power feedback control mode (FIG. 3E) such that output of a fiber laser beam FB rises substantially from zero or a value around zero to a preceding level having no substantial effect on laser processing and arrives at a desired level (PA) for the laser processing from a preceding level PB after a first time period (preceding pulse width TB) has elapsed (time point t2 of FIGS. 3A to 3F) from the start of the rising to the preceding level (time point t1 of FIGS. 3A to 3F), and this may effectively prevent occurrence of a high-peak pulse HP at the rising edge of the fiber laser beam FB (FIG. 3F).

Abstract: A laser driver circuit comprising a current supply circuit for supplying a laser diode with a current is provided. The current supply circuit comprises a voltage-to-current converter circuit, a current output line for outputting the current generated by the voltage-to-current converter circuit, a current supply line connected to the laser diode, a ground line connected to the ground, and a current path switch for selectively connecting either the current supply line or the ground line to the current output line. The laser driver circuit further comprises a current output prevention circuit for preventing the voltage-to-current converter circuit from generating the current by disconnecting the voltage input line using a voltage input switch so that the voltage is not input to the voltage-to-current converter circuit, when the current output line and the ground line are connected by the current path switch.

Abstract: The present invention provides a method of fabricating a beam formatting diode laser using a surface-emitting distributed feedback (SE-DFB) laser array (SELA), instead of edge-emitting diodes that provides a brighter diode and results in simple and few optical components to reduce the complexity and cost of solid-state laser pump modules and direct-diode applications.

Abstract: A method of estimating an injection power of seed light injected into an injection-seeded transmitter. A back face monitoring (BFM) response of the injection-seeded transmitter is determined, and data representative of the BFM response stored in a memory. During run-time, a controller of the injection-seeded transmitter, detects a temperature of the injection-seeded transmitter and an instantaneous BFM current. BFM response data is obtained from the memory based on the detected temperature, and the seed light injection power estimated based on the obtained data and the detected instantaneous BFM current.

Abstract: A method of protecting a laser against damage caused by undesired incident light in a resonator includes measuring a parameter, which is a measure for the optical power of the incident light. In more concrete terms, the optical power occurring at a resonator mirror is measured. In response to a result of the measurement, a pumping power for the laser is reduced to reduce the optical power in the resonator to a value that is uncritical for the laser.

Abstract: The light sources according to the present invention include a laser oscillator including a semiconductor laser, a drive circuit for the semiconductor laser, an ACC circuit, an APC circuit, and a switch, and a starting drive current storage device, and is controlled in such a manner that the driving current at the start of the laser driving be always constant, and after the start of the lighting, it is switched to the APC operation to carry out the power control of the laser light output.

Abstract: In an exposure device comprising a laser controller that is configured as a circuit board capable of independently being changed, and that controls the emission of laser light from a laser emitter emitting laser light on receipt of an instruction for control given from a main controller responsible for overall control of the operation of the exposure device, error control information that is obtained in advance with regard to the circuit board and controls variations of a controlling factor due to a circuit error of the circuit board is stored into a memory provided to the laser controller prior to the provision of the circuit board to the exposure device. On receipt of an instruction for control given from the main controller to cause the emission of laser light in a predetermined amount of light, the laser controller determines a condition of emission of laser light based on the error control information stored in the memory to cause the laser emitter to emit laser light under the condition of emission.

Abstract: In a modulated optical reflectance (MOR) system, a laser noise suppression technique utilizes a reference beam split optically from a probe laser prior to injection of a beam from the probe laser into an MOR signal path. The reference beam and a probe beam reflected from the sample are sent to first and second detectors, which produce first and second signals. A signal combiner receives the second signal at a first input and produces a combiner signal that corresponds to a difference between signals applied to the first and a second input. A level balancer receives the first signal and a signal derived from the combiner signal and produces a balancer output that is coupled to the second input of the signal combiner. The combination of the balancer output and the second signal tends to cancel out an average value of the second signal from the combiner signal.

Abstract: A laser scanning microscope (LSM) having variable light intensity and a control method for the same. The light intensity of a laser beam in an LSM has been controlled to date with high accuracy, but also high costs by means of an acousto-optic component (AOM, AOTF). According to the invention, such a component for beam modulation is to be omitted, without reducing the exposure accuracy of the sample. In an LSM, a directly modulated laser diode (10) is used with an electric control (12) for direct modulation. Said laser diode (10) has a turn-on delay of the light intensity that is dependent on the amount of the control variable when subjected to an electric control variable. The control (12) is designed such that the fluctuation width (??tV) of the occurring turn-on delay (?tV) is smaller than 1 ?s, particularly smaller than 0.5 ?s. Thus highly exact modulation without an acousto-optic component is possible.

Abstract: According to aspects of an embodiment of the disclosed subject matter, a line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control method and apparatus are disclosed which may comprise a bandwidth metrology module measuring the bandwidth of a laser output light pulse beam pulse produced by the light source and providing a bandwidth measurement; a bandwidth error signal generator receiving the bandwidth measurement and a bandwidth setpoint and providing a bandwidth error signal; an active bandwidth controller providing a fine bandwidth correction actuator signal and a coarse bandwidth correction actuator signal responsive to the bandwidth error. The fine bandwidth correction actuator and the coarse bandwidth correction actuator each may induce a respective modification of the light source behavior that reduces bandwidth error. The coarse and fine bandwidth correction actuators each may comprise a plurality of bandwidth correction actuators.

Abstract: A laser diode driver IC of a transmitter or transceiver is provided with circuitry for monitoring the forward voltage of the laser diode or laser diodes of the transmitter or transceiver to enable the health of the laser diode or diodes to be assessed in real-time.

Abstract: The present invention provides a laser diode driving circuit that enables to precisely control the amplitude of the driving current with suppressing the overshoot and the undershoot appeared in the monitor signal of the optical output from the laser diode. The driving circuit of the invention includes a signal mixer, a comparator, an averaging unit and a current generator. The signal mixer superposes an additional signal on the monitor signal. The amplitude of the additional signal varies in accordance with a preset distribution function. The comparator compares thus superposed signal with a reference level and outputs a binary signal. The averaging unit integrates this binary signal and the current generator provides the driving current based on the averaged binary signal.

Abstract: A driving device including a light emitter, a biasing circuit, a light receiver, an automatic control system, and an alternating current (AC) path is disclosed. The light emitter generates an optical signal. The biasing circuit generates a driving signal to activate the light emitter such that the light emitter operates in a working range. The light receiver detects the output power of the optical signal for generating a corresponding electrical signal. The automatic control system adjusts the driving signal according to the corresponding electrical signal such that the output power of the optical signal approaches a preset value. The AC path is coupled between the light emitter and an external signal source for receiving at least one AC modulated signal such that the light emitter generates at least one modulated optical signal.

Abstract: A laser output power command determination value from a controller (17) is input to an upper limit current determination unit (32), and an upper limit current value to be decided based on the laser output power command determination value is determined. Then, a second comparator (30) compares a command current value determined from the laser output power command determination value and a laser output power command determination value measured with a power monitor (13), with an upper limit current value determined with a upper limit current determination unit (32). The second comparator (30) determines a command current value when the upper limit current value is greater than the command current value and the upper limit current value when the command current value is greater than the upper limit current value, as a reference current value, by which reference current value a current to be supplied to pumping means is configured to be controlled.

Abstract: A multi-beam laser light-intensity control circuit includes laser diodes; a light-receiving element for receiving a laser beam emitted from each laser diode and outputting a current corresponding to the light intensity of the received laser beam; and an automatic power control circuit for automatically controlling output power of each laser diode based on the current output from the light-receiving element.

Abstract: Provided is an optical analyzer which can promote enhancement of measurement sensitivity, cost reduction, size reduction, structural flexibility, disturbance resistance, and the like, at the same time. A laser device to be used in such optical analyzer is also provided. An optical analyzer comprises a laser light source (2); a wavelength selection element (3) for selecting and leading out light having a wavelength substantially equal to the absorption wavelength of an analysis object from among light outputted from the laser light source (2); an optical detection means (5) for detecting the intensity of light red out from the wavelength selection element (3); and a drive current control means (6) for increasing or decreasing the drive current of the laser light source (2) near a specified current value thereof for outputting light of the absorption wavelength, and setting the drive current at such a current value as the intensity of light detected by the optical detection means (5) has a peak value.

Abstract: A system contains a laser output measurement circuit used in a laser control system (210). The circuits contain a photodiode (109), sample and hold amplifier (202), IC with synchronizer and delay circuits (206), and an analog to digital converter (204). The circuits measure the laser light output (107) while the laser Module (106) transmits signals. The measurement circuit tracks and stores the laser light output (107) signal using a Photodiode Sensor (109) and with a Sample/hold (202). The methods calculate the value of the laser light output (107) from mathematical relationships, which correlate the light output (107) of the laser Module (106) to the current value of the drive signal (100). Some of the distinguishing features in the present invention are 1) feedback information from the photodiode is obtained in a synchronous manner as a snapshot of the laser performance, and 2) the measurements are precise and calibrated, and 3) no disruption of the signal transmission occurs.

Abstract: An optical transmitter and a method to control the transmitter are disclosed, in which the optical output may be substantially maintained even in the inactive state of the input burst signal. The optical transmitter includes the APC feedback control and the detector that senses the active and inactive states of the input burst signal. When the transition to the inactive state is detected, the controller enters the second APC mode in which only the bias current is adjusted so as to maintain the optical output to be a preset value. The normal APC feedback control may be recovered after a preset period from the practical transition of the input burst signal from the inactive state to the active state.

Abstract: A light source system for delivery of light including a light source having an output arranged to emit light in an output path, the output path including an unguided section and an at least partially transmissive optical component wherein the optical component provides at least one residual reflection when the system is in use and a detector system is arranged to detect said residual reflection. The detector is in one embodiment arranged to produce at least one feedback response arranged to stabilize the optical output of the light source system. Hereby a feedback may be implemented with little or no reduction of performance.

Abstract: A semiconductor laser is a distributed feedback semiconductor laser in which the lasing wavelength can be changed, and includes a semiconductor substrate and a semiconductor layer portion provided on the substrate and including first and second active layers and an intermediate layer that optically couples the first active layer and the second active layer. The first active layer, the intermediate layer, and the second active layer are arranged in that order in a predetermined axis direction. The semiconductor laser further includes a diffraction grating that is optically coupled with the first and second active layers of the semiconductor layer portion, a first electrode and a second electrode for injecting carriers into the first active layer and the second active layer, respectively, and a third electrode for supplying the intermediate layer with a current. The grating extends in the predetermined axis direction and has a period that is uniform in the predetermined axis direction.

Abstract: According to aspects of an embodiment of the disclosed subject matter, a line narrowed high average power high pulse repetition laser micro-photolithography light source bandwidth control method and apparatus are disclosed which may comprise a bandwidth metrology module measuring the bandwidth of a laser output flight pulse beam pulse produced by the light source and providing a bandwidth measurement; a bandwidth error signal generator receiving the bandwidth measurement and a bandwidth setpoint and providing a bandwidth error signal; an active bandwidth controller providing a fine bandwidth correction actuator signal and a coarse bandwidth correction actuator signal responsive to the bandwidth error. The fine bandwidth correction actuator and the coarse bandwidth correction actuator each may induce a respective modification of the light source behavior that reduces bandwidth error. The coarse and fine bandwidth correction actuators each may comprise a plurality of bandwidth correction actuators.

Abstract: Semiconductor diode lasers are phase-locked by direct current injection and combined to form a single coherent output beam. The optical power is amplified by use of fiber amplifiers. Electronically control of the optical phases of each emitter enables power efficient combining of output beams to be maintained under dynamic conditions.

Abstract: A disclosed laser diode driving device drives laser diodes with driving currents obtained by adding switch currents to corresponding bias currents and includes a common switch current generating circuit configured to generate a common switch current according to an input signal; switch current generating circuits provided for the corresponding laser diodes and configured to generate the switch currents based on the common switch current and input signals; switches configured to control the output of the switch currents to the corresponding laser diodes according to input signals; bias current generating circuits configured to generate the bias currents and output the generated bias currents to the corresponding laser diodes; and a control unit configured to detect the light intensities of the respective laser diodes and to control the common switch current generating circuit, the switch current generating circuits, and the switches to adjust the light intensities of the respective laser diodes.

Abstract: A control system for a laser source driven by a direct current drive voltage includes a system control board, a laser driver, and a power stabilizing circuit. The system control board is configured to output a control signal based on input data. The laser driver is coupled to the laser source and to the system control board. The laser driver is configured to drive the laser source with the drive voltage to generate a laser beam modulated according to the control signal. The power stabilizing circuit is configured to regulate the drive voltage to a given constant level. The power stabilizing circuit includes a first circuit and a second circuit. The first circuit is configured to boost the drive voltage to a level exceeding the given constant level. The second circuit is configured to limit the boosted drive voltage to the given constant level.

Abstract: A laser projector including a green diode pumped microchip laser module projecting a green laser beam, an optical sensor receiving the laser beam, a power control circuit for the green diode pumped microchip laser module receiving a signal from the optical sensor relative to the power output of the laser beam, and control electronics receiving the signal from the optical sensor connected to the power control circuit modulating the power output of the green diode pumped microchip laser module to maintain a substantially constant power output from the green diode pumped microchip laser module.

Abstract: A method for a laser system to compensate a variability of a signal converter in the laser system includes generating a temperature signal corresponding to a temperature of a laser and adjusting a signal of the signal converter based on at least the temperature signal. A laser transceiver includes a memory, a controller, a bandwidth circuit, and a modulation driver. The controller generates at least one control signal set by a host in the memory. The bandwidth circuit is a programmable low-pass filter (LPF) receiving the control signal and at least one input terminal receiving at least one data signal. The programmable LPF filters the data signal based on the control signal. The modulation driver has at least one input terminal receiving the filtered data signal. The modulation driver provides a modulation current to a laser in response to the filtered data signal.

Abstract: A method and apparatus are disclosed for controlling bandwidth in a multi-portion laser system comprising a first line narrowed oscillator laser system portion providing a line narrowed seed pulse to an amplifier laser system portion, may comprise utilizing a timing difference curve defining a relationship between a first laser system operating parameter other than bandwidth and the timing difference and also a desired point on the curve defining a desired timing difference, wherein each unique operating point on the curve corresponds to a respective bandwidth value; determining an actual offset from the timing difference at the desired point on the curve to an actual operating point on the curve; determining an error between the actual offset and a desired offset corresponding to a desired bandwidth; modifying the firing differential timing to remove the error between the actual offset and the desired offset.

Abstract: An apparatus for analyzing, identifying or imaging an target including an integrated dual laser module coupled to a pair of photoconductive switches to produce cw signals in the range of frequencies from 100 GHz to over 2 THz focused on and transmitted through or reflected from the target; and a detector for acquiring spectral information from signals received from the target and using a multi-spectral homodyne process to generate an electrical signal representative of some characteristics of the target with resolution less than 250 MHz. The photoconductive switches are activated by laser beams from the dual laser module. The lasers in the module are tuned to different frequencies and have two distinct low frequency identification tones respectively that are used in conjunction with a stable optical filter element to permit precise determination of the offset frequency of the lasers.

Abstract: The temperature of a laser diode changes in response to video content across a line of a displayed image, and the radiance changes as a function of temperature. An adaptive model estimates the temperature of the laser diode based on prior drive current values. For each displayed pixel, diode drive current is determined from the estimated diode temperature and a desired radiance value. A feedback circuit periodically measures the actual temperature and updates the adaptive model.

Abstract: A power monitoring system uses a low loss reflective element to partially split the output laser beams from an array of laser sources, in a parallel configuration, to produce a monitor beams for each laser source. Each of these monitor beams may propagate within the reflective element in a lossless manner under total internal reflection and into one of a plurality of photodiodes that sense an optical characteristic such as output beam intensity, where this sensed signal is then used as part of a feedback control to control operation of the laser sources in the array.

Abstract: A laser generator includes a generation means for pumping by a pumping light source (7) a pumping medium (3) to generate a fundamental-wave laser beam, an output sensor (6) for measuring average output power or pulse energy of the fundamental-wave laser beam, a wavelength-conversion element (5), arranged on an optical path for the fundamental-wave laser beam, for converting the fundamental-wave laser beam into its higher-harmonic-wave laser beam, and a controller (9) for memorizing a determination value set to a value lower than a breakage threshold for average output power or pulse energy of the laser beam converted by the wavelength-conversion element (5), and for, when the measurement value becomes not lower than the determination value, controlling the output power of the fundamental-wave laser beam to be a value lower than the breakage threshold; thereby, the beam intensity through the wavelength-conversion element (5) never exceeds the breakage threshold, and thus breakage of the wavelength-conversion e

Abstract: A method of controlling a semiconductor laser that has a plurality of wavelength selection portions having a different wavelength property from each other and is mounted on a temperature control device, including: a first step of correcting a temperature of the temperature control device according to a detected output wavelength of the semiconductor laser; and a second step of controlling at least one of the wavelength selection portions so that changing amount differentials between each wavelength property of the plurality of the wavelength selection portions is reduced, the changing amount differential being caused by correcting the temperature of the temperature control device.

Abstract: A light transmitter and an auto-control circuit thereof are provided. The circuit includes a driving module and a feedback module. The driving module is coupled to the feedback module and a load. The driving module provides a driving current for driving the load. The feedback module provides a bias signal to the driving module according to the change of the temperature, for adjusting the driving current and stabilizing an output power.