tailieunhanh - Micromechanical Photonics - H. Ukita Part 4

Tham khảo tài liệu 'micromechanical photonics - h. ukita part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 50 2 Extremely Short-External-Cavity Laser Diode b 0 Effective reflectivity Fig. . Dependence of side-mode suppression ratio on Rf a and dependence of spectrum line width on Rf b . Tunable LD A vertical cavity surface-emitting laser VCSEL diode or a light-emitting diode LED with a micromechanical reflector can be used in tuneO devices . The structure is designed to have an air gap of approximately one wavelength. When a voltage is applied to the membrane reflector the electrostatic force reduces the air gap which in turn reduces the wavelength. An edge-emitting LD is also applicable for micromechanically tunable LDs . Recent micromachining tchhnoiggh bin made it east Id 6111 1 I lie need for lens and fiber systems for guiding the light to a PD or a moving mechanism leadingto the integration of optics mechanics and electronics. Structure The edge-emitting tunable laser diode consists of a laser diode LD1 a microcantilever MC driven photothermally by an LD2 Fig. . The light emitted from LD2 onto the side wall of the MC is partially absorbed heating Applications 51 the MC and producing the bending moment. At ixo onanl frequency the ICC is excited easily due to the thermal stress caused by a pulsed laser beam from LD2. This sideways vibration varies the external-cavity-length Lex between the MC wall and the LD1 facet and there is so little incident light from the LD1 that it has no effect on the MC vibration. The variation of Lex causes the wavelength shift of the LD1. Manufacturing Method An MC and the LDs were fabricated on a GaAs substrate. There are three micromachining proeesees mvoleed m íabricatígg the MC 1 ae cl ch-si op layer of AlGaAs is formed in the LD structure prepared by metalorganic vap or phase epitaxy MOVPE . 2 The microstructure shape is precisely defined by a reactive dry-etching RIBE technique which dll simukaneously form the vertical etched .