Abstract: A wavelength detector is described. The wavelength detector includes a beamsplitter having a wedged back surface with respect to the front surface to reflect the incoming optical signal into two paths. Filters, at least one of which varies with wavelength of the optical signal are in each of the said paths. The filtered light in the two paths is detected by a photodetector and the output electrical signals are log amplified. The log amplified signals are applied to a difference amplifier whose output is indicative of the wavelength or polarization of the incident optical signal.

Abstract: A laser absorption spectrometer for making measurements of absorption spectra which includes a wavelength sensor that can measure the average wavelength of pulses from a laser on a pulse-by-pulse basis and that can measure the internal wavelength variation of laser pulses. The laser absorption spectrometer can be used with pulsed lasers like the quantum cascade laser to perform sensitive measurements of the absorption spectra even when there is pulse-to-pulse variation of average wavelength and when there are internal changes in the wavelength of the pulses.

Abstract: A wavelength detector is described. The wavelength detector directs an incoming optical signal into two paths, at least one of which varies with wavelength of the optical signal. The light in the two paths is detected by a photodetector and the output electrical signals are log amplified. The log amplified signals are applied to a difference amplifier whose output is indicative of the wavelength of the incident optical signal.

Abstract: A laser absorption spectrometer for making measurements of absorption spectra which includes a wavelength sensor that can measure the average wavelength of pulses from a laser on a pulse-by-pulse basis and that can measure the internal wavelength variation of laser pulses. The laser absorption spectrometer can be used with pulsed lasers like the quantum cascade laser to perform sensitive measurements of the absorption spectra even when there is pulse-to-pulse variation of average wavelength and when there are internal changes in the wavelength of the pulses.

Abstract: An analog detection system for determining a ring-down rate or decay rate 1/&tgr; of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

Abstract: A wavelength detector is described. The wavelength detector includes a beamsplitter having a wedged back surface with respect to the front surface to reflect the incoming optical signal into two paths. Filters, at least one of which varies with wavelength of the optical signal are in each of the said paths. The filtered light in the two paths is detected by a photodetector and the output electrical signals are log amplified. The log amplified signals are applied to a difference amplifier whose output is indicative of the wavelength or polarization of the incident optical signal.

Abstract: A wavelength detector is described. The wavelength detector directs an incoming optical signal into two paths, at least one of which varies with wavelength of the optical signal. The light in the two paths is detected by a photodetector and the output electrical signals are log amplified. The log amplified signals are applied to a difference amplifier whose output is indicative of the wavelength of the incident optical signal.

Abstract: An analog detection system for determining a ring-down rate or decay rate 1/&tgr; of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

Abstract: An analog detection system for determining a ring-down rate or decay rate 1/&tgr; of an exponentially decaying ring-down beam issuing from a lifetime or ring-down cavity during a ring-down phase. Alternatively, the analog detection system determines a build-up rate of an exponentially growing beam issuing from the cavity during a ring-up phase. The analog system can be employed in continuous wave cavity ring-down spectroscopy (CW CRDS) and pulsed CRDS (P CRDS) arrangements utilizing any type of ring-down cavity including ring-cavities and linear cavities.

Abstract: Distinct locking and sampling light beams are used in a cavity ring-down spectroscopy (CRDS) system to perform multiple ring-down measurements while the laser and ring-down cavity are continuously locked. The sampling and locking light beams have different frequencies, to ensure that the sampling and locking light are decoupled within the cavity. Preferably, the ring-down cavity is ring-shaped, the sampling light is s-polarized, and the locking light is p-polarized. Transmitted sampling light is used for ring-down measurements, while reflected locking light is used for locking in a Pound-Drever scheme.

Abstract: An inexpensive semi enclosed alternator provides high power prolonged operation in environments having particle contamination in the ambient atmosphere. An alternator housing has front and rear housing portions, and a drive shaft carrying a rotor assembly is within the housing. A drive shaft extension from the housing holds a fan assembly. The rear housing portion has cylindrical sidewalls joined to a closed end portion 27 and forms an air sealed cavity except for an open end facing the front housing portion. The front housing portion comprises cylindrical sidewalls, having through-openings therein, which terminate in a first end opening 31, facing rear housing open end 28, and a substantially open second end opening 30 facing the fan assembly and the ambient atmosphere. Preferably rotor and stator assemblies, and rectifying diodes, are positioned within the housing substantially between the through openings and the closed end portion of the rear housing.