A new type of phase-locked laser diode interferometer that uses self-mixing interference in the optical system is described. The selfmixing interference (SMI) signal is obtained easily by optical feedback, i.e., feeding back the laser beam from the object to the laser diode (LD). The SMI signal can be detected by a photodiode in the package of the LD. Therefore, a beamsplitter, reference mirror, and external photodetector are not required, and an interference signal is obtained using a simple optical system. Although the mechanism of SMI is completely different from that of conventional interference, it is shown that the response of the SMI signal to phase changes is the same as that of conventional interference. We used the phase-locked technique to fix the phase change and demonstrated measurement of absolute distance and displacement.

A design of prototype Infra-Red High-dispersion Spectrograph (IRHS) is described. IRHS is a cryogenic echelle spectrometer for 8.2-m Subaru Telescope, which will operate at 8 to 13 µm with resolving power of 200,000. To achieve such a high dispersion and broad bandwidth, a Germanium immersion echelle grating was adopted. As a preliminary step, we started to develop the proto-type of IRHS (ProtoIRHS) with currently available Ge immersion grating (30×30×72 mm) and one 512×412 Si:As impurity band detector array, which will provide the maximum resolving power of 50,000 at 10 µm with slit width of 0.612 arcseconds (0.48 mm) and two-pixels sampling.

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