Abstract: A gas leak detector includes a solar detector and a signal filter. The solar detector generates an electrical response by interfering a light signal with a solar signal and detecting a resultant interference signal. The signal filter is communicatively coupled to the solar detector and filters the electrical response to isolate a beat-note signal. The beat-note signal has an amplitude that is inversely related to a concentration of a species that forms a gaseous plume located along a path of the solar signal.

Abstract: A combustion-zone chemical sensing system (100) is disclosed that includes pitch reflective optics (110) that collimate MIR electromagnetic energy from an input fiber (150), a reflector (120), catch reflective optics (112) that focus reflected MIR electromagnetic energy into an output fiber (152), and a detector (140) to detect MIR electromagnetic energy from the output fiber. An optical head (102) for sensing a combustion zone (104) is disclosed that includes pitch reflective optics (110) that collimate MIR electromagnetic energy from an input fiber (150) towards a reflector (120), catch reflective optics (112) that focus MIR electromagnetic energy, reflected from the reflector, into an output fiber (152), and an alignment housing that interfaces with structure adjacent the combustion zone.

Abstract: A demultiplexed filtering method includes propagating an optical beam from an input optical fiber to a diffraction grating to produce a first and a second diffracted beam having a respective first center wavelength ?1 and a second center-wavelength ?2>?1 of the optical beam. The first diffracted beam propagates back toward the input optical fiber at a first diffracted angle determined in part by ?1 and a diffraction order m1 of the first diffracted beam. The second diffracted beam propagates back toward the input optical fiber at a second diffracted angle determined in part by ?2 and a diffraction order m2<m1. The method also includes (i) coupling the first diffracted beam into a first optical fiber of a one-dimensional optical-fiber array that includes the input optical fiber, and (ii) coupling the second diffracted beam into a second optical fiber of the one-dimensional optical-fiber array.

Abstract: A tunable diode laser absorption spectroscopy (TDLAS) optical head includes a housing configured for attachment to a sight tube attached to a wall of a process chamber. The TDLAS optical head further includes optics within the housing for transmitting, receiving, or transmitting and receiving a laser beam within a process chamber through the sight tube. The TDLAS optical head further includes a photo sensor in the housing positioned to receive light emitted by combustion within the process chamber to which the housing is attached.

Abstract: A tunable diode laser absorption spectroscopy (TDLAS) optical head includes a housing configured for attachment to a sight tube attached to a wall of a process chamber. The TDLAS optical head further includes optics within the housing for transmitting, receiving, or transmitting and receiving a laser beam within a process chamber through the sight tube. The TDLAS optical head further includes a photo sensor in the housing positioned to receive light emitted by combustion within the process chamber to which the housing is attached.

Abstract: A method of monitoring blockage of a sight tube attached to a wall of a process chamber, the sight tube being operatively associated with a TDLAS optical head with a window between the sight tube and the TDLAS optical head. The method includes the steps of providing a photo sensor in the TDLAS optical head, the photo sensor being positioned to receive light emitted by a light emitting process within the process chamber. An emission signal produced by light emitted by the light emitting process within the process chamber being received by the photo sensor is monitored. A determination is made if the emission signal is degrading.

Abstract: A method of monitoring blockage of a sight tube attached to a wall of a process chamber, the sight tube being operatively associated with a TDLAS optical head with a window between the sight tube and the TDLAS optical head. The method includes the steps of providing a photo sensor in the TDLAS optical head, the photo sensor being positioned to receive light emitted by a light emitting process within the process chamber. An emission signal produced by light emitted by the light emitting process within the process chamber being received by the photo sensor is monitored. A determination is made if the emission signal is degrading.

Abstract: A method of absorption spectroscopy to determine a rapidly variable gas parameter. The method includes transmitting light from a synchronization light source to a synchronization detector. The transmitted light is periodically interrupted by a moving mechanical part between the synchronization light source and synchronization detector. The output from the synchronization detector is used to generate a repeating time signal having variable phase delay. This signal is used to control the timing of laser spectroscopy wavelength scans. Multiple spectroscopic scans may be repeated at multiple selected time signal phase delay and the results averaged for each phase. Apparatus for implementing the above methods are also disclosed.

Abstract: A method of absorption spectroscopy to determine a rapidly variable gas parameter. The method includes transmitting light from a synchronization light source to a synchronization detector. The transmitted light is periodically interrupted by a moving mechanical part between the synchronization light source and synchronization detector. The output from the synchronization detector is used to generate a repeating time signal having variable phase delay. This signal is used to control the timing of laser spectroscopy wavelength scans. Multiple spectroscopic scans may be repeated at multiple selected time signal phase delay and the results averaged for each phase. Apparatus for implementing the above methods are also disclosed.

Abstract: An inexpensive, robust, and adhesive-free method and apparatus is disclosed for efficiently coupling first and second optical components together utilizing a flexure assembly for fine alignment. An initial three-dimensional rough alignment process positions the first and second optical components proximate to each other and aligns them in three dimensions. The first and second components are then misaligned by a fixed amount, causing a defocus, and then securely fastened together. The fine alignment process uses standard machine screws, or other easily attainable, robust tensioning means to progressively increase the tension around the periphery of the flexure assembly, which causes the flexure to bend and the second optical component to translate along the longitudinal axis of the flexure assembly and tilt with respect to the longitudinal axis of the flexure assembly, which re-focuses and three-dimensionally finely aligns the optical components for optimum coupling efficiency in a simple and secure manner.

Abstract: An inexpensive, robust, and adhesive-free method and apparatus is disclosed for efficiently coupling first and second optical components together utilizing a flexure assembly for fine alignment. An initial three-dimensional rough alignment process positions the first and second optical components proximate to each other and aligns them in three dimensions. The first and second components are then misaligned by a fixed amount, causing a defocus, and then securely fastened together. The fine alignment process uses standard machine screws, or other easily attainable, robust tensioning means to progressively increase the tension around the periphery of the flexure assembly, which causes the flexure to bend and the second optical component to translate along the longitudinal axis of the flexure assembly and tilt with respect to the longitudinal axis of the flexure assembly, which re-focuses and three-dimensionally finely aligns the optical components for optimum coupling efficiency in a simple and secure manner.

Abstract: A low noise laser includes a birefringent gain crystal arranged so that polarization is not constant within the gain crystal. The gain crystal and an intracavity optical element each have a nonzero polarization retardance. The total single-pass retardance is approximately equal to an odd multiple of one-half wave; for example each may provide one quarter wave retardance. In one embodiment the optical element comprises a nonlinear crystal situated within the laser cavity for Type II frequency doubling. The principal crystal axis of the gain crystal is offset from the principal axis of the nonlinear crystal at an offset angle for example about 45°. In one embodiment a gain crystal and frequency-doubling crystal are coupled together to form a monolithic laser component. An alternative embodiment is described in which the optical element comprises a quarter-wave plate and the laser output includes substantially two linear polarizations at the fundamental wavelength.

Abstract: A low noise laser includes a birefringent gain crystal arranged so that polarization is not constant within the gain crystal. The gain crystal and an intracavity optical element each have a nonzero polarization retardance. The total single-pass retardance is approximately equal to an odd multiple of one-half wave; for example each may provide one quarter wave retardance. In one embodiment the optical element comprises a nonlinear crystal situated within the laser cavity for Type II frequency doubling. The principal crystal axis of the gain crystal is offset from the principal axis of the nonlinear crystal at an offset angle for example about 45°. In one embodiment a gain crystal and frequency-doubling crystal are coupled together to form a monolithic laser component. An alternative embodiment is described in which the optical element comprises a quarter-wave plate and the laser output includes substantially two linear polarizations at the fundamental wavelength.