Far-field, linewidth and thermal characteristics of a high-speed 1550-nm MEMS tunable VCSEL

Abstract

We report an electrically pumped 1550 nm MEMS tunable VCSEL with a continuous tuning of 101 nm at 22 °C. The top MEMS-DBR with built-in stress gradient within the dielectric layers is deposited in a low-temperature PECVD chamber on an InP-based half-VCSEL, structured by surface-micromachining and electrothermally actuated for continuous wavelength tuning. With 2.6 mA threshold current, the laser shows maximum CW output power of 3.2 mW at 1560 nm. The MEMS-VCSEL operates in single-mode with SMSR > 39 dB across the entire tuning range. At 36 °C, the tuning range reaches up to 107 nm. The divergence angle of the MEMS-VCSEL is approximately 5.6° for all tuning wavelengths. The intrinsic linewidth of an unpackaged device is 21 MHz. Quasi-error-free operation at 12.5 Gbps using a directly modulated MEMS-VCSEL is reported for a record 60 nm tuning, showing the potential of the so-called colorless source in WDM applications.

Systematic characterization of a 1550 nm microelectromechanical (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) with 7.92 THz tuning range for terahertz photomixing systems

“…However, a minimum SMSR of >50 dB is maintained over the entire tuning range, which is 11 dB higher than the value presented in Ref. 16. The minimum VCSEL voltage obtained with I MEMS % 24 mA corresponds to the lowest threshold gain.…”

“…This decreases the Q-factor of the cavity, but it also increases the outcoupled power since the transmission T ¼ 1 À R t , with R t being the reflectivity of the membrane. However, thermal rollover with increased injection current 16 appears much earlier when compared with the point of minimum threshold gain. Despite obtaining more power with I inj > 20 mA, we limit the injection current to I inj ¼ 20 mA to avoid thermal rollover during THz photomixing.…”

“…Therefore, an ESA displaying the DSH signal D DSH has weighted contributions from both Gaussian and Lorentzian profiles and is fitted by a Voigt profile, from which the linewidth D is calculated according to Ref. 16,…”

“…Therefore, the substrate temperature of VCSEL-B is changed from 22 C to 28 C. The increase in substrate temperature results in a large blueshift of the emission wavelength for MEMS-VCSEL. 16,27 The reason is that the thermal expansion of the half-VCSEL materials is greater than that of the membrane dielectrics. The consequent greater lateral expansion of the half-VCSEL pulls down the suspended mirror, decreasing the air gap, i.e., blueshifting the emission wavelength.…”

Beyond 25 Gb/s Directly-Modulated Widely Tunable VCSEL for Next Generation Access Network

“…In this paper, we present for the first time the exploitation of a long-wavelength widely tunable vertical-cavity surface-emitting laser (VCSEL) [3] to achieve a colorless ONU transmitter, presenting low-cost and reduced footprint. Discrete multitone modulation (DMT) combined with direct detection (DD) is employed to use limited-bandwidth VCSELs and standard receivers suitable for 10 Gb/s operation, targeting a transported upstream (US) capacity greater than 25 Gb/s up to 40-km standard single-mode fiber (SSMF) without any chromatic dispersion (CD) compensation.…”