In this paper an on-chip device capable of wavelength-selective generation of vortex beams is demonstrated. The device is realized by integrating a spiral phase-plate onto a MEMS tunable Fabry-Perot filter. This vortex-MEMS filter, being capable of functioning simultaneously in wavelength and orbital angular momentum (OAM) domains at around 1550 nm, is considered as a compact, robust and cost-effective solution for simultaneous OAM- and WDM optical communications. Experimental spectra for azimuthal orders 1, 2 and 3 show OAM state purity >92% across 30 nm wavelength range. A demonstration of multi-channel transmission is carried out as a proof of concept.
In this work, we have used a tunable VCSEL for high-speed optical data transmission. To obtain wide tunability, a MEMS-DBR is surface micromachined onto a short-cavity high-speed VCSEL operating at 1550 nm. Ultra-wide continuous tuning is realized with electro-thermal actuation of the MEMS with built-in stress gradient
within SiO<sub>x</sub>/SiN<sub>y</sub> dielectric layers. The MEMS-VCSEL operates in single-mode with SMSR > 40 dB across the entire tuning range. Quasi-error-free transmission of direct-modulation at record 15 Gbps is reported for 20 nm tuning, showing the potential towards the standard requirements for the SFP+ modules in the tail-ends of the WDM transmission system.
With the use of SiO<sub>2</sub>/SiC based movable MEMS-DBR, the continuous tuning range of electrically pumped MEMS-VCSEL can be extended to > 140 nm. The high refractive index contrast of Δn > 1 between SiO<sub>2</sub> and SiC reduces the needed number of layers (11 layers) and broadens the spectral width of the reflectivity (448nm for R > 99.5 %) by more than a factor of two compared to the material system SiO<sub>2</sub>/Si<sub>3</sub>N<sub>4</sub> (23 layers / 216nm for R > 99.5 %), which has been used for the current world record continuous tuning range of 100nm of an electrically pumped MEMS-VCSEL. The smaller number of needed DBR-layers enables a significant reduction of the overall mirror thickness, which enables a further miniaturization of the device and thus an increase of the free spectral range (FSR), the ultimate limit for continuous wavelength tuning. In this paper we evaluate the performance advantages of using SiO<sub>2</sub>/SiC based MEMS-DBR for tunable VCSEL by using Transfer-matrix method simulations.
In this paper, we demonstrate for the first time the far-field experimental results and the linewidth characteris-
tics for widely tunable surface-micromachined micro-electro-mechanical system (MEMS) vertical-cavity surface-
emitting lasers (VCSELs) operating at 1550 nm. The fundamental Gaussian mode emission is confirmed by
optimizing the radius of curvature of top distributed Bragg reflector (DBR) membrane and by choosing an ap-
propriate diameter of circular buried tunnel junctions (BTJs) so that only the fundamental Gaussian mode can
sustain. For these VCSELs, a mode-hop free continuous tuning over 100 nm has already been demonstrated,
which is achieved by electro-thermal tuning of the MEMS mirror. The fiber-coupled optical power of 2mW over
the entire tuning range has been reported. The singlemode laser emission has more than 40 dB of side-mode
suppression ratio (SMSR). The smallest linewidth achieved with these of MEMS tunable VCSELs is 98MHz
which is one order of magnitude higher than that of fixed-wavelength VCSELs.
We present surface micro-machined micro-electro mechanical-system (MEMS) tunable vertical-cavity surfaceemitting
lasers (VCSEL) with rectangular and triangular shaped quantum wells (QWs) emitting around 1:95 μm
predestined for broadband tunable diode laser absorption spectroscopy. The VCSELs show single-mode operation
and high side-mode suppression-ratio SMSR < 50 dB within the whole tuning range of 50nm and 35 nm, the
fibre-coupled optical power of 1:0mW and 1:76mW and the threshold current of 2:5mA and 2:0mA for the
rectangular and triangular shaped QWs respectively. The 3 dB modulation frequency of the MEMS is 110 Hz.
A mode hop free single mode tuning < 90nm at 40°C and 45nm at 70°C is demonstrated with a MEMS tunable VCSEL for the first time. The device shows a fiber-coupled output power of 2.9mW at 20°C and 0.5mW at 70°C. The side mode suppression ratio is larger than 40 dB over the entire tuning and temperature range of up to 70°C. The presented technology is cost effective and thus capable for mass production. It is applicable for tuneable VCSELs operating in different wavelength regimes, which are limited by the absorption of the DBR materials only.