An atomic absorption apparatus using a laser for producing a light beam having a characteristic frequency f, typically ranging from several MHz to several GHz, and a characteristic polarization for measuring the absorption of that light beam by atoms of interest. The apparatus has a modulator to generate a modulating signal to modulate the characteristic frequency f and produce a phase-modulated light beam. The apparatus includes a domain where the specific atoms are located. This domain is positioned in the path of the phase-modulated light beam such that the phase-modulated light beam encounters the specific atoms when passing through the domain and some of the specific atoms absorb a portion of the phase-modulated light beam. Typically, the domains containing the atoms of interest include process chambers for vacuum coating, ion milling, sputtering, mass spectroscopy vapor coating or deposition, and the like. The amount of light absorbed depends on the motion of the atoms relative to the phase-modulated light beam.

In a dye laser comprising a cavity, one end of which is closed by an angular dispersion system, and which is provided with a separator for extracting the laser beam from the cavity, the separator is arranged so that the dispersive system and the system for application of the laser beam are on the same side relative to the separating face of the separator. An aperture isolates the reference wavelength from the extracted beam. Such a laser can have very good monochromaticity and is useful wherever there is a need for high spectral purity, in particular in Raman spectrometry.

By incorporating a phase-conjugating process (Stimulated Brillouin Scatteg) with a master oscillator power amplifier laser cavity, a new phase conjugate resonator (PCR) is obtained. The PCR utilizes flashlamp-pumped dye lasers and a resonator cavity that is formed by a 100% mirror on one end and a Stimulated Brillouin Scattering (SBS) cell on the other end. The SBS cell functions as one of the mirrors of the resonator and causes the entire system to operate as a phase conjugate resonator. The result is vastly improved (an order of magnitude) beam qualities over conventional resonators for large lamp systems.

Two collocated, weakly coupled probes, on loop and one dipole, detect the magnetic and electric fields inside a maser cavity. Signals from the probes are compared in phase, and the signal output from the phase detector is applied to a varactor, the reactance of which is coupled into the cavity by a microwave coupler. Alternatively, the varactor may be placed inside the cavity. Any deviation of phase from 90.degree. as detected by the phase detector will then produce an error signal that will change the reactance coupled into the resonant cavity to change its reactance, and thus correct its resonance frequency. An alternative to using two probes is to use a single disk probe oriented to detect both the magnetic and electric fields, and thus provide the error signal directly.

A rapidly tunable laser system which is operative to tune the laser beam emission to a predetermined wavelength in accordance with the polarization state thereof is disclosed. The laser beam emission may be tuned between predetermined wavelengths as rapidly as it can be altered between polarization states. More specifically, the laser system includes a polarization modulator for modulating the radiation beam emitted from a laser cell between at least two polarization states, and at least two diffraction gratings which are uniquely and fixedly aligned to specularly reflect and retroreflect radiation incident thereupon. The retroreflected radiation is of a wavelength uniquely identified with the angle of incidence of the corresponding diffraction grating. One diffraction grating retroreflects radiation at one wavelength and response to one polarization state of the radiation beam, and the other diffraction grating retroreflects radiation at another wavelength in response to radiation at another polarization state. Hence, the laser system may be tuned between the one and another wavelengths by modulating the radiation beam between the one and another polarization states by the polarization modulator. The laser beam emission may be tuned between the predetermined wavelengths as rapidly as it can be altered between the polarization states.