Abstract: A method and apparatus for scanning and testing optical components is disclosed. An incident laser beam is directed at a trihedral retroreflector and is redirected by the trihedral retroreflector onto a test surface. The trihedral retroreflector is movable in X and Y directions over the test surface, in a plane perpendicular to the incident beam, scanning the incident beam over the test surface. The reflected beam from the test surface is redirected by the trihedral retroreflector to measurement instrumentation including a photodetector. If the test surface is planar, the reflected beam retraces the path of the incident beam independent of the translation of the trihedral retroreflector. Irregularities in the test surface cause deflections of the reflected beam. The linear scanning range, in both X and Y direction, of a single trihedral retroreflector of diameter "d" is the value (d times 2). The linear scanning range of a series of "n" trihedral retroreflectors of diameter "d" is the value (d times 2.sup.n).

Abstract: The invention relates to the generation of lased light having a broadband spectral content within a frequency-shifted feedback cavity containing a gain medium, a frequency-shifting device and one or more mirrors so arranged that they receive the multiple-frequency output issuing from the gain medium and repeatedly circulate it around the cavity through both the gain medium and frequency-shifter thereby either increasing or decreasing the frequency of the circulating beam by an incremental amount without any Fabry-Perot frequency discrimination, mode production or chirping during each pass. Each frequency-shifted signal is combined with those preceding it to output a modeless beam of broad spectral output. By selectively mismatching the cavity length and the frequency shift per pass, a continuous wave output is assured; whereas, conversely, by phasing the circulating frequency-shifted beams within limits amounting to several percent plus or minus the optimum, a pulsed output results.

Abstract: This invention relates to an improved method for producing pulsed trains of light within a cavity which comprises repeatedly incrementally increasing the frequency of a constant wave of light circulating within the cavity and combining the frequency-shifted beams to produce at least one pulsed train output thereof. This can be done in either a passive or active cavity.

Abstract: Frequency stabilization is disclosed for a two-mode laser, such as a Zeeman aser. The emission frequency of the laser is servo-stabilized to the center of the atomic gain curve to provide a stable laser reference frequency that is independant of time and enviromental operating conditions. Stabilization in a longitudinal-field Zeeman laser is achieved by utilizing the mode-pulling effect which makes the frequency difference between the two circular polarization components have a parabolic dependence on the optical frequency of the laser. The detected intermode beat frequency from the laser is subjected to digital phase-sensitive, drift-free integration, utilizing a reversible counter, to provide a cumulative count with a rate of increase corresponding to the displacement of the average wavelength from the atomic center wavelength and an analog error-correction signal is generated therefrom which is coupled to the laser.

Abstract: A method of and apparatus for measuring the wavelength of a source of radiant energy which includes passing split beams generated by such source along the same paths as those from a source of known wavelength and then comparing the number of interference fringes developed by the two sources as an element in one common path is varied in its disposition.