Athermal and tunable operations of 850 nm vertical cavity surface emitting lasers with thermally actuated T-shape membrane structure

Abstract

We demonstrate the athermal operation and the wavelength tuning of 850 nm GaAs-based vertical cavity surface emitting lasers with a thermally actuated cantilever structure. The thermal actuation of a top distributed Bragg reflector mirror enables us to compensate the temperature drift of lasing wavelengths. The temperature dependence of lasing wavelengths could be controlled from −0.011 nm/K to −0.18 nm/K by changing the cantilever length. In addition, a T-shape membrane structure was introduced for efficient electro-thermal tuning. A small temperature dependence of −0.011 nm/K and wavelength tuning of 4 nm were obtained.

Tuning Characteristics of Monolithic MEMS VCSELs With Oxide Anti-Reflection Layer

“…Comparing λ/ T and λ/ P, the temperature rise of a micromachined cantilever per applied heating power T/ P is estimated to be 4.6 K/mW. It is reasonably in agreement with the theoretical value (8.4 K/mW) estimated from finite-element thermal simulation neglecting heat spreading in air [11].…”

“…Therefore the efficiency of our MEMS VCSEL is more than 4 times larger than their MEMS VCSELs. It is due to large λ/ T and a smaller heater with better thermal management as described in [11]. The efficiency can be further improved by shortening the cavity length.…”

“…Wavelength tuning is achieved by changing the cavity length via the mechanical actuation of the top mirror. The top mirror of our MEMS VCSEL is actuated by using a bimorph effect in the thermal actuator which is composed of AlGaAs DBR and gold film [11], [12]. Namely, a temperature increase makes the cantilever to bend downward because of its large difference in thermal expansion coefficients.…”

GaAs/AlGaAs-Based 870-nm-Band Widely Tunable Edge-Emitting V-Cavity Laser

“…Semiconductor lasers in this wavelength window commonly employ GaAs/AlGaAs based quantum well (QW) active regions, although high performance 850-nm diode lasers with high speed and high temperature characteristics have been achieved by using strained QWs based on AlInGaAs [5], InGaAsP [6], and InGaAs [7] due to improved differential gain in the active regions. At present, tunable semiconductor lasers in this wavelength range have been relatively immature as compared to commercially available InPbased telecom 1550 nm-band widely tunable lasers which commonly employ complex grating structures such as sampled grating distributed Bragg reflectors (SGDBR) [8], [9], although diffraction grating based external cavity lasers [4], [10], [11], micro-electro-mechanical system (MEMS) based vertical cavity surface emitting laser (VCSEL) [1], [12], [13], and distributed Bragg reflector (DBR) laser [14]- [16] have been reported. For external cavity lasers, wide tuning range has been achieved, but their large size and high packaging cost have limited their applications mainly to laboratory instruments.…”