Rotating shutters: a mechanical way of flattening gaussian beam profiles in time average.

A mechanical method of flattening the Gaussian intensity distribution of laser beams in time average is presented. Specially shaped rotating shutters are the key feature of this method, which has been applied to achieve homogeneous submicrometer patterning of macroscopically large samples by laser interference exposure. This method represents a simple yet useful alternative to applying beam broadening or degaussing plates (apodizing filters).

Free-running 9.1-microm distributed-feedback quantum cascade laser linewidth measurement by heterodyning with a C18O2 laser.

We report spectral linewidth measurements of a 9.1-microm distributed-feedback quantum cascade laser (QCL). The free-running QCL beam was mixed with a waveguide isotopic C18O2 laser onto a high-speed HgCdTe photomixer, and beat notes were recorded from a radio-frequency spectral analyzer.