Abstract: An isotopomer absorption spectral analyzing apparatus and its method for precisely measuring the isotope ratio by substantially equalizing the absorption signal levels of different species of isotopes. In an isotopomer absorption spectral analyzing apparatus, a sample cell (21) capable of providing optical paths of different optical lengths is installed, optical beams A, B are caused to enter the sample cell (21) and travel along paths of different optical lengths, thereby determining the abundance ratio between species of isotopes in molecules from the ratio between intensities of signals corresponding to the species of isotopes.

Abstract: A gas detection device employs a tunable wavelength laser, modulated about an absorption line of a gas to be detected. By measuring the ratio of the fundamental to the second harmonic of the modulation frequency, the detection is independent of the optical path length. This permits an aimable device in which a laser beam is directed toward a remote surface, reflected thereby, and the reflected beam focused upon a detector. The presence of the gas to be detected in the space between the device and the reflective surface is thereby determined.

Abstract: A light source has a tunable wavelength single mode semiconductor laser. The laser outputs a single mode laser beam having a wavelength tuned in accordance with a drive current and emits, for an object to be detected, at least a first laser beam having a first wavelength which is absorbed by a gas to be detected and a second laser beam having a second wavelength which is not absorbed by the gas to be detected. A controller switches the drive current having a predetermined value corresponding to the first or second wavelength at a predetermined period and supplies the drive current to the laser and controls the drive current having the predetermined value corresponding to the first or second wavelengths so that the first or second laser beams are alternately output from the laser with substantially the same power while the first and second wavelengths are maintained.

Abstract: A dual-wavelength laser apparatus includes a laser emitting a laser beam consisting of two wavelength components, a methane cell for controlling and equalizing gains of the two wavelength components, a cavity length modulator including a piezoelectric element for periodically modulating the cavity length of the laser, and a feedback circuit for controlling the modulation center such that the sum of outputs of the two modulated wavelength components is kept substantially constant. The feedback circuit includes a detector for detecting a laser output, a lock-in amplifier for detecting and amplifying an output from the detector, an integrator for integrating an output from the lock-in amplifier, and a high-voltage amplifier for generating a bias voltage set by the integrator.