Design and Experiment of 3-Dimensional Micro-Optical System for MEMS Tunable Lasers

Abstract

This paper presents a 3-dimensional micro-optical system for improving the optical coupling efficiency in the external cavity tunable lasers. It is constructed by an optical fiber and a curved mirror; the former acts as a rod lens to transform the light in one direction while the latter converges the light in the other direction. Compared with the previous MEMS lasers that have no light focusing or only in one direction, this 3D micro-optical system allows for long external cavity length and high coupling efficiency, which are critical for wide tuning range. A prototype is fabricated on SOI wafer by DRIE with an etching depth of 75 µm. It obtains a coupling efficiency as high as 46.5% with a total external cavity length of 220 µm. In contrast, the coupling efficiency is only 13% when the fiber rod lens is absent, and is 1% when no light transformation is involved. Compared with conventional laser optical systems that employ external ball lenses and other optical components, this 3D micro-optical system possesses the advantages of simple packaging, large alignment tolerance and easy mass production.

Analysis of micromachined Fabry-Pérot cavities using phase-sensitive optical low coherence interferometry: Insight on dimensional measurements of dielectric layers

“…The impact of these geometrical parameters is manifested experimentally, with an actual effective cavity length, L eff , quite different from the physical length of the cavity L phys . Though this concept of effective length was thoroughly studied in several micro-photonic components involving combinations of semiconductor and air layers, 13, 14 the situation is quite different in our case because the change of materials is concentrated at the vicinity of the mirror, which consists here of silicon-air Bragg reflectors. In other words, one can define in our case, two virtual interfaces inside the Bragg reflector stacks and the resonating optical cavity behaves as if light bounces between these virtual interfaces.…”

Characteristics of micromachined injection locking lasers

“…1 where the master laser provides an external locking source for the slave laser. In this paper, the master laser is a MEMS tunable external-cavity laser [9][10], and its wavelength is tuned by using MEMS movable curved mirror.…”

Retro-reflection VOA using parabolic mirror for low insertion loss and linear attenuation relationship

“…The traveling distance of the rays from the input to the output is 1100 µm. To avoid the divergence of the rays in the vertical direction, a normal SMF (diameter 125 µm) is use as the rod lens [13]. Otherwise the insertion loss will be at least 13 dB, too large to make the PVOA practical.…”