With the use of SiO2/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 SiO2 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 SiO2/Si3N4 (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 SiO2/SiC based MEMS-DBR for tunable VCSEL by using Transfer-matrix method simulations.
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.
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.
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 report the investigation of the state of polarization (SOP) of a tunable vertical-cavity surface-emitting laser
(VCSEL) operating near 850 nm with a mode-hop free single-mode tuning range of about 12 nm and an amplitude
modulation bandwidth of about 5 GHz. In addition, the effect of a sub-wavelength grating on the device and
its influence on the polarization stability and polarization switching has been investigated. The VCSEL with an
integrated sub-wavelength grating shows a stable SOP with a polarization mode suppression ratio (PMSR) more
than 35 dB during the tuning.
We present a micro electro-mechanical system (MEMS) tunable vertical-cavity surface-emitting laser (VCSEL) emitting
around 1.55 μm with single-mode output power of >2.5mW and high side-mode suppression-ratio (SMSR) of >50dB
over the entire tuning range of >50nm. The small-signal modulation technique (S21) has been used to study intrinsic and
parasitic influences on the modulation response of the device. Additionally, the static characteristics as well as electrical
and thermal design of the device are discussed with respect to its high-speed modulation behavior. The tunable laser
shows 3-dB direct modulation frequencies above 6.4 GHz.
Long-wavelength VCSELs with emission wavelengths beyond 1.3 μm have seen a remarkable progress over the last
decade. This success has been accomplished by using highly advanced device concepts which effectively overcome the
fundamental technological drawbacks related with long-wavelength VCSELs such as inferior thermal properties and
allow for the realization of lasers with striking device performance. In this presentation, we will give an overview on the
state of the technology for long-wavelength VCSELs in conjunction with their opportunities in applications for optical
sensing. While VCSELs based on InP are limited to maximum emission wavelengths around 2.3 μm, even longer
wavelengths up to the mid-infrared range beyond 3 μm can be achieved with VCSELs based on GaSb. For near-infrared
InP-based VCSELs, the output characteristics include sub-mA threshold currents, up to several milliwatts of singlemode
output power and ultralow power consumption. New concepts for widely tunable VCSELs with tuning ranges up to
100 nm independent from the material system for the active region are also presented. Today, optical sensing by Tunable
Diode Laser Spectroscopy is a fast emerging market. Gas sensing systems are used for a wide range of applications such
as industrial process control, environmental monitoring and safety applications. With their inherent and compared to
other laser types superior properties including enhanced current tuning rates, wavelength tuning ranges, modulation
frequencies and power consumption, long-wavelength VCSELs are regarded as key components for TDLS applications.
We present surface micro-machined tunable vertical-cavity surface-emitting lasers (VCSELs) operating around
1550nm with tuning ranges up to 100nm and side mode suppression ratios beyond 40 dB. The output power
reaches 3.5mW at 1555 nm. The electro-thermal and the electro-statical actuation of a micro electro-mechanical
system (MEMS) movable distributed Bragg reflector (DBR) membrane increases/decreases the cavity length
which shifts the resonant wavelength of the cavity to higher/lower values. The wavelength is modulated with
200 Hz/120 kHz. Both tuning mechanisms can be used simultaneously within the same device. The newly
developed surface micro-machining technology uses competitive dielectric materials for the MEMS, deposited
with low temperature plasma enhanced chemical vapor deposition (PECVD), which is cost effective and capable
for on wafer mass production.
Widely tunable vertical cavity surface emitting lasers (VCSEL) are of high interest for optical communications,
gas spectroscopy and fiber-Bragg-grating measurements. In this paper we present tunable VCSEL operating at
wavelength around 850 nm and 1550 nm with tuning ranges up to 20 nm and 76 nm respectively. The first versions
of VCSEL operating at 1550 nm with 76 nm tuning range and an output power of 1.3mW were not designed for
high speed modulation, but for applications where only stable continious tuning is essential (e.g. gas sensing).
The next step was the design of non tunable VCSEL showing high speed modulation frequencies of 10 GHz with
side mode supression ratios beyond 50 dB. The latest version of these devices show record output powers of
6.7mW at 20 °C and 3mW at 80 °C. The emphasis of our present and future work lies on the combination of
both technologies. The tunable VCSEL operating in the 850 nm-region reaches a modulation
bandwidth of 5.5GHz with an output power of 0.8mW.