Abstract: A non-spectral computed tomography scanner includes a radiation source configured to emit x-ray radiation, a detector array configured to detect x-ray radiation and generate non-spectral data, and a memory configured to store a spectral image module that includes computer executable instructions including a neural network trained to produce spectral volumetric image data. The neural network is trained with training spectral volumetric image data and training non-spectral data. The non-spectral computed tomography scanner further includes a processor configured to process the non-spectral data with the trained neural network to produce spectral volumetric image data.

Abstract: An injection seeding laser system in which the seeded laser has a monolithic structure without any moving parts. The seeder emits light whose wavelength is swept in a radio frequency (RF) over a range that covers one or more longitudinal mode(s) of the seeded laser, which eliminates the need for active cavity length control and phase locking between the injected and output signals. The gain medium of the seeded laser is an active medium whose population is substantially inversed in response to an excitation, which can be electrical or optical. Time synchronization between the injected seeds and the triggering signal to the slave is generally not required. The present invention enables fiber MOPO that produces high power laser pulses in an efficient and cost-effective manner.

Abstract: A method for improving spectral, spatial, and temporal stability of semiconductor lasers and their beam profile uniformity based on statistical average of plural transient or unsteady state longitudinal and lateral modes that are continuously perturbed. A laser module implementing the method comprises a semiconductor laser, a drive circuit generating RF-modulated drive current, and an automatic power control loop for producing stable, low noise and uniform or nearly uniform illumination field along one or two dimensions.

Abstract: An all-solid-state laser system produces coherent DUV radiation through a third or fourth harmonic generation. The fundamental wavelength is generated by a slave laser optically pumped by one or more light source(s) of high density array(s) and is stabilized by injecting optical seeds whose wavelength is rapidly swept to cover the fundamental wavelength. The pump effects are enhanced by a pump chamber that recycles unabsorbed pump light. The present invention enables DUV pulses with a width shorter than 1 ns and a repetition rate higher than 100 kHz. The output DUV wavelength is adjustable by selecting an appropriate seeder.

Abstract: An efficient and low-noise solid-state laser is optically pumped by one or more laser diode(s) driven by RF modulated current. The solid-state laser operation is stabilized by the pump source stable in both spectrum and intensity, in conjunction with automatic power control wherein the feedback loop accurately reflects the true drift in the output power. Moreover, the pump efficiency is optimized and the optical noise is minimized by adjusting the diode operation temperature such that the pump wavelength coincides with the absorption peak of the gain medium. By internally or externally modulating the amplitude of the drive current, the pump diode(s) operate in pulsed mode with controllable shape, width, repetition rate, and pulse-to-pulse intervals, which enables essentially constant optical energy produced from each pulse of the solid-state laser in high repetition rates with variable pulse-to-pulse intervals.

Abstract: A self-contained module injects seeds into a slave laser for applications such as single mode or multimode injection seeding, master oscillator power amplifiers, regenerative amplifiers, optical parametric oscillators, Raman lasers, and LIDAR systems. The injection source provides a continuous wavelength sweeping for master-slave resonance to replace conventional cavity length control of the slave laser and phase locking schemes. The inventive module can be operated remotely as a separate unit or be packaged as a subsystem in the injection seeding system. The salve can be used as it is. Modifications of the slave laser and/or additional efforts are not needed.

Abstract: An all-solid-state laser system produces coherent DUV radiation through a third or fourth harmonic generation. The fundamental wavelength is generated by a slave laser optically pumped by one or more light source(s) of high density array(s) and is stabilized by injecting optical seeds whose wavelength is rapidly swept to cover the fundamental wavelength. The pump effects are enhanced by a pump chamber that recycles unabsorbed pump light. The present invention enables DUV pulses with a width shorter than 1 ns and a repetition rate higher than 100 kHz. The output DUV wavelength is adjustable by selecting an appropriate seeder.

Abstract: A method for effective injection seeding is based on continuous wavelength sweeping for matching the injected seeds with one or more longitudinal mode(s) of the slave oscillator in every pump pulse. This is achieved through rapidly varying laser drive current resulted from RF modulation. Depending on the modulation parameters, the seed may be operated at quasi-CW or pulsed mode, with a narrow or broad bandwidth, for injection seeding of single longitudinal mode or multimode. The wavelength and bandwidth of the laser output can be tuned according to the needs. From pulse to pulse, the master-slave resonance may occur at different wavelengths upon cavity length fluctuations. Cavity length control via complicated feedback devices and phase locking schemes are consequently not required.

Abstract: A method for producing low-noise laser output at wavelengths ranging from IR through visible to UV in various operation modes from a monolithic microchip laser comprises schemes of (1) generating one or two fundamental beam(s) from light source(s) selected upon the desired wavelength(s), polarization(s), and other features related to the desired laser output; (2) intracavity beam combination/separation due to the walk-off effect in one or more birefringent crystal(s) transparent to the propagating lights and highly anisotropic; (3) wavelength conversion in one or more nonlinear optical crystal(s); (4) compact and efficient pump source(s); and (5) minimization of intracavity loss/noise. One resonator cavity supports only one fundamental beam, which eliminates the green problem. The gain media can be selected from an extensive group of materials including isotropic and naturally birefringent crystals, with polarization dependent or independent laser emissions.

Abstract: A method for producing low-noise laser output at various wavelengths and/or in various operation modes in a monolithic microchip laser comprises schemes of generating two fundamental beams in separate cavities, precise intracavity beam combination based on the walk-off effect in birefringent crystal, and wavelength conversion in nonlinear optical crystals. The fundamental beams are produced from light sources selected upon the desired wavelengths, polarizations, and other features related to the laser output. Low-noise laser devices operated in SLM or with spectra of flat-top or desired bandwidths are constructed according to the method. High-volume fabrication is feasible. Apparatus of compact size and efficient frequency conversion is demonstrated with various configurations including those for generating low-noise 491 nm laser, as a replacement of Argon ion laser.

Abstract: Solid-state laser(s) pumped by incoherent, monochromatic light from sources such as LED arrays and integrating technologies such as high power LED arrays and solid-state laser materials in conjunction with efficient and uniform absorption of pumping energies through a diffusing pump chamber. The resulting laser(s) are compact, robust, low-cost, and able to produce high power output for practical applications. It may efficiently operate over wide temperature and performance ranges, at CW or pulse modes, even with ultra short pulse width and/or extremely high repetition rates. Our inventive structure(s) is/are highly flexible and applicable to a large group of lasing media including those with very short upper state life times. Advantageously, they may be applied to a plethora of laser systems at wavelengths that have important applications and unavailable to other direct pumping technologies.

Abstract: An efficient and low-noise solid-state laser is optically pumped by one or more laser diode(s) driven by RF modulated current. The solid-state laser operation is stabilized by the pump source stable in both spectrum and intensity, in conjunction with automatic power control wherein the feedback loop accurately reflects the true drift in the output power. Moreover, the pump efficiency is optimized and the optical noise is minimized by adjusting the diode operation temperature such that the pump wavelength coincides with the absorption peak of the gain medium. By internally or externally modulating the amplitude of the drive current, the pump diode(s) operate in pulsed mode with controllable shape, width, repetition rate, and pulse-to-pulse intervals, which enables essentially constant optical energy produced from each pulse of the solid-state laser in high repetition rates with variable pulse-to-pulse intervals.

Abstract: An injection seeding laser system in which the seeded laser has a monolithic structure without any moving parts. The seeder emits light whose wavelength is swept in a radio frequency (RF) over a range that covers one or more longitudinal mode(s) of the seeded laser, which eliminates the need for active cavity length control and phase locking between the injected and output signals. The gain medium of the seeded laser is an active medium whose population is substantially inversed in response to an excitation, which can be electrical or optical. Time synchronization between the injected seeds and the triggering signal to the slave is generally not required. The present invention enables fiber MOPO that produces high power laser pulses in an efficient and cost-effective manner.

Abstract: A low-noise laser diode module comprises a laser diode for emitting light with a wavelength in the range from UV to IR, a drive circuit for injecting electrical current into said diode, and an automatic power control circuit for monitoring and adjusting laser output power using front-facet photodiode external to the laser assembly and a feedback loop. Said drive circuit produces injection current modulated by an RF signal with variable degrees, depending on the wavelength to be stabilized, the desired spectral bandwidths of the laser output, and/or other applications. Said RF signal can be a sine wave, a distorted sine wave, a rectified sine wave, a non-sine wave, a series of narrow pulses, or repetitive shunt. The present invention encompasses a method for producing stable, broadband, and low-coherent laser. The present invention also encompasses a method for producing stable narrowband or single longitudinal mode laser.

Abstract: A method for reducing speckle noise of a monolithic microchip laser with intracavity beam combining and sum frequency mixing is based on time averaging of uncorrelated speckle patterns generated from a large number of independent longitudinal modes and comprises schemes including selection of gain media and nonlinear optical materials to support broadband sum frequency mixing; adoption of gain-conjugated and/or chirped mirrors for flat-top spectra and/or mode phase diversification; multimode laser operation introduced by RF modulation; and multiplication of source modes in frequency mixing process featured with degeneration free and narrowed/uneven intervals. A device and an apparatus for generating low speckle noise red, green, blue lasers adaptable for color display systems are developed based on the inventive method.

Abstract: Solid-state lasers pumped by incoherent or partially coherent, monochromatic light sources such as high power VCSEL arrays. Efficient and uniform injection of pumping energy into gain medium is achieved through spectral match of the pump source with the gain medium absorption and multi-bounce reflections of unabsorbed pump light in a diffusing pump chamber. One preferred embodiment of the diffusing pump chamber is a hollow cylinder coaxially surrounding the gain medium. One or more transparent windows, slit-shaped or otherwise, for transmission of pump light are evenly distributed around the perimeter of the chamber and are parallel to the axis. Another preferred embodiment of the diffusing pump chamber is a highly reflecting compound parabolic concentrator. A 2-D VCSEL array is employed as the pump source and the gain medium is located at the focusing point of the chamber.

Abstract: A method for effective injection seeding is based on continuous wavelength sweeping for matching the injected seeds with one or more longitudinal mode(s) of the slave oscillator in every pulse. This is achieved through rapidly varying laser drive current, as a result of RF modulation. Depending on the modulation parameters, the seeder may be operated in CW or quasi-CW or pulsed mode, with a narrow or broad bandwidth, for injection seeding of single longitudinal mode or multimode. The wavelength and bandwidth of the laser output can be tuned according to the needs. Injection seeding of high repetition rates is achievable. From pulse to pulse, the master-slave resonance persists though may occur at different longitudinal modes upon cavity length fluctuations. Cavity length control and phase locking schemes are consequently not required.

Abstract: A method, an apparatus, and a module for producing dual beam from a single laser diode provide for means of simultaneously pumping two individual gain media with orthogonal polarizations. A beam splitter splits the emissive laser beam into two portions based on the polarization. A polarization control element or mechanism adjusts the polarization and the intensity ratio of the separated beam portions. Applications to monolithic microchip lasers include generating new wavelengths based on intracavity beam combining and mixing.

Abstract: A method for reducing speckle noise of a monolithic microchip laser with intracavity beam combining and sum frequency mixing is based on time averaging of uncorrelated speckle patterns generated from a large number of independent longitudinal modes and comprises schemes including selection of gain media and nonlinear optical materials to support broadband sum frequency mixing; adoption of gain-conjugated and/or chirped mirrors for flat-top spectra and/or mode phase diversification; multimode laser operation introduced by RF modulation; and multiplication of source modes in frequency mixing process featured with degeneration free and narrowed/uneven intervals. A device and an apparatus for generating low speckle noise red, green, blue lasers adaptable for color display systems are developed based on the inventive method.

Abstract: A self-contained module injects seeds into a slave laser for applications such as single mode or multimode injection seeding, master oscillator power amplifiers, regenerative amplifiers, optical parametric oscillators, Raman lasers, and LIDAR systems. The injection source provides a continuous wavelength sweeping for master-slave resonance to replace conventional cavity length control of the slave laser and phase locking schemes. The inventive module can be operated remotely as a separate unit or be packaged as a subsystem in the injection seeding system. The salve can be used as it is. Modifications of the slave laser and/or additional efforts are not needed.