Abstract: A single longitudinal mode laser in the present invention is described with an external high resolution filter to select a single longitudinal mode as the laser output from a multiple longitudinal mode microchip laser. The high resolution filter comprises at least one grating and a plurality of optical components to disperse the multiple longitudinal modes of the microchip laser and select a single longitudinal mode. The high resolution filter may have a single, double, triple, or quadruple-pass structure, which causes the laser beam to be diffracted by the grating once, twice, three, or four times, respectively, for increased resolution. The grating is configured to have a diffraction angle at the up-limit of 80 to 90 degrees for the single pass structure and to have the near up-limit diffraction angle of 73 to 90 degrees for the double, triple, and quadruple-pass structure.

Abstract: A triangle delay line (or interferometer) for providing a variable time delay for two laser beam comprises a fixed arm having one mirror and a variable arm having a beam splitter and a mirror mounted on a translation stage for adjusting the time delay. The variable arm has to move at a specific direction which in general is different from the longitude direction of the laser beam. The means to determine the moving direction and to calculate the time delay by moving the translation stage have been provided. A single shot autocorrelator based on the triangle delay line is very compact and easy to use. Also a grating delay line comprising a grating, a retroreflection mirror, and a output steering mirror can provide a variable time delay distributed along the beam cross section up to a nanosecond. A single shot autocorrelator utilizing the grating delay line can measure the laser pulse up to hundreds picosecond.

Abstract: A tunable time plate device for providing a continually adjustable time delay between two linearly polarized laser pulses .omega..sub.1 and .omega..sub.2. The device comprises a time plate made of a parallel flat birefringence crystal having a principal axis of refractive index n.sub.z parallel to its surface, and a principal axis of refractive index n.sub.x having an angle .phi. to its surface normal. The time plate is rotatably mounted such that it is rotatable about its n.sub.z principal axis for tuning a time delay between the two laser pulses as they travel through the time plate which is a function of an incident angle .theta. between its surface normal and the propagation direction of the laser pulses. The time delay therefore can be continually adjusted by rotating said time plate to change said incident angle .theta..