Integrated multiwavelength laser source module with micromachined mirrors

An integrated silicon sub-mount for laser diodes is reported. The objective of this work is to develop a miniaturized laser source module with switchable wavelengths to use a common optics for different optical data storage media. Patterned thick photoresist: SU-8 is adopted as a micromirror structure in conjunction with proper mirror coating with thin metal film. Photolithographically defined and pre-aligned micromirrors potentially offer an enhanced degree of freedom to optical MEMS designer and greatly reduce the misalignment errors in assembling the optical components. Mesa-shaped mounting seats for assembling the laser diodes, tall vertical sidewall mirrors for reflecting the laser beams emitted from the laser diodes, and deep trench not to disturb the reflected laser beams are integrated on a silicon sub-mount chip by micromachining. The average surface roughness of the metal coated SU-8 sidewall mirrors is well below 1/20 wavelength of the incident laser light of interest, smooth enough for CD or DVD applications. The insertion loss of the vertical sidewall mirror is measured as -0.77 dB when the wavelength of the reflected laser beam is 650 nm.