Compact GaSb/silicon-on-insulator 2.0x mu m widely tunable external cavity lasers

2.0x mu m widely tunable external cavity lasers realized by combining a GaSb gain chip with a silicon photonics waveguide circuit for wavelength selection are demonstrated. Wavelength tuning over 58 nm from 2.01 to 2.07 mu m is demonstrated. In the silicon photonic integrated circuit, laser feedback is realized by using a silicon Bragg grating and continuous tuning is realized by using two thermally tuned silicon microring resonators (MRRs) and a phase section. The uncooled laser has maximum output power of 7.5 mW and threshold current density of 0.8 kA/cm(2). The effect of the coupling gap of the MRRs on tunable laser performance is experimentally assessed. A side mode suppression ratio better than 52 dB over the full tuning range and in the optimum operation point of more than 60 dB is achieved for the laser with weakly coupled MRRs. (C) 2016 Optical Society of Americ

Hybrid GaSb/Si swept-wavelength laser sensor technology for next generation wearable healthcare device platform

Spectral region beyond 1.7 mu m is particularly interesting for biomedical spectroscopic sensing applications due to the presence of strong and molecule-specific ro-vibrational overtone and combination absorption bands for a number of important analytes such as glucose, lactate, urea, human serum albumin among others. However, this spectral region has been largely unexplored for applications targeting wearable device technology due to the absence of commercially available semiconductor light source technology. In this work we report on recent progress in developing beyond-state-of-the-art GaSb-based swept-wavelength laser technology as a key building-block of the proposed spectroscopic sensor concept. To demonstrate the capability of the technology, we provide experimental data of in vitro sensing concentrations down to the normal physiological range and beyond for glucose, lactates, urea and bovine serum albumin. Furthermore, we provide initial experimental evidence of non-invasive in vivo sensing experiment with extracted absorbance signature of human serum albumin collected from the wrist and demonstrate a clear path towards sensing other analytes. Finally, to demonstrate the full potential of the spectroscopic sensor technology for the wearable device market, we present results of our initial effort to realize a complete spectroscopic sensor system-on-a-chip based on hybrid GaSb/Si material platform and manufactured using conventional 200 mm silicon-on-insulator CMOS technology process in a commercial high-volume foundry

III–V-on-silicon photonic integrated circuits for spectroscopic sensing in the 2–4 μm wavelength range

The availability of silicon photonic integrated circuits (ICs) in the 2-4 mu m wavelength range enables miniature optical sensors for trace gas and bio-molecule detection. In this paper, we review our recent work on III-V-on-silicon waveguide circuits for spectroscopic sensing in this wavelength range. We first present results on the heterogeneous integration of 2.3 mu m wavelength III-V laser sources and photodetectors on silicon photonic ICs for fully integrated optical sensors. Then a compact 2 mu m wavelength widely tunable external cavity laser using a silicon photonic IC for the wavelength selective feedback is shown. High-performance silicon arrayed waveguide grating spectrometers are also presented. Further we show an on-chip photothermal transducer using a suspended silicon-on-insulator microring resonator used for mid-infrared photothermal spectroscopy

Terahertz quantum cascade laser implementing a {hacek over (C)}erenkov difference-frequency generation scheme

A terahertz source implementing a {hacek over (C)}erenkov difference-frequency generation scheme in a quantum cascade laser. The laser includes an undoped or semi-insulating InP substrate with an exit facet that is polished at an angle between 10° to 40°. The laser further includes a first waveguide cladding layer(s) in contact with an active layer (arranged as a multiple quantum well structure) and a current extraction layer on top of the substrate. Furthermore, the laser includes a second waveguide cladding layer(s) on top of the active layer, where the first and second waveguide cladding layers are disposed to form a waveguide structure by which terahertz radiation generated in the active layer is guided inside the laser. The terahertz radiation is emitted into the substrate at a {hacek over (C)}erenkov angle relative to a direction of the nonlinear polarization wave in the active layer, and once in the substrate, propagates towards the exit facet.Board of Regents, University of Texas Syste

III-V/silicon photonic integrated circuits for spectroscopic sensing in the 2 mu m wavelength range (invited paper)

III-V/silicon photonic integrated circuits (ICs) promise to enable low cost and miniature optical sensors for trace-gas detection, bio-sensing and environmental monitoring. A lot of these applications can benefit from the availability of photonic ICs beyond the telecommunication wavelength range. The 2 mu m wavelength range is of interest for spectroscopic detection of many important gases and blood constituents. In this contribution we will present 2 mu m-wavelength-range III-V/silicon photonic ICs consisting of tunable laser sources, photodetectors and silicon waveguide circuits. Silicon waveguides with a loss of similar to 0.5 dB/cm are obtained in a well-established silicon photonics platform. Based on the waveguides, low insertion loss (2-3 dB) and low crosstalk (25-30 dB) arrayed waveguide gratings (AWGs) are realized for the 2.3 mu m wavelength range. Active opto-electronic components are integrated on the photonic IC by the heterogeneous integration of an InP-based type-II epitaxial layer stack on silicon. III-V-on-silicon 2.3 mu m range distributed feedback (DFB) lasers can operate up to 25 degrees C in continuous-wave regime and shows an output power of 3 mW. By varying the silicon grating pitch, a DFB laser array with broad wavelength coverage from 2.28 mu m to 2.43 mu m is achieved. III-V-on-silicon photodetectors with the same epitaxial layer stack exhibit a responsivity of 1.6 A/W near 2.35 mu m. In addition, we also report a 2 mu m range GaSb/silicon hybrid external cavity laser using a silicon photonic IC for wavelength selective feedback. A wavelength tuning over 58 nm and side mode suppression ratio better than 60 dB is demonstrated

Widely tunable III–V/silicon lasers for spectroscopy in the short-wave infrared

Integrating III-V gain material with silicon photonic integrated circuits enables the realization of advanced laser sources and full integrated systems for optical communication and sensing applications. The availability of III-V/silicon laser sources operating in the 2-2.5 mu m short-wave infrared wavelength range is very valuable for spectroscopic sensing since many important industrial gases and blood glucose have absorption bands in this wavelength range. In this paper, first we present our latest results on heterogeneously integrated III-V-on-silicon distributed feedback (DFB) laser arrays. A III-V-on-silicon DFB laser array covering the 2.27-2.39 mu m wavelength range with 6 nm wavelength spacing is reported. This DFB laser array is employed as the light source for tunable diode laser absorption spectroscopy of different gases. A four-channel DFB laser array integrated with a beam combiner is used to perform spectroscopic sensing over a 7 nm spectral range without mode hopping at room temperature. Finally, we present our recent advances in widely tunable Vernier lasers based on heterogeneous integration and butt-coupling of the gain section. Continuous tuning near the absorption lines by thermally adjusting the laser cavity length enables high-resolution tunable diode laser absorption spectroscopy measurements together with wide wavelength coverage

III-V/Si photonic integrated circuits for the mid-infrared

We review our work on SOI and Ge-on-SOI PICs for the mid-infrared. We demonstrate the integration of III-V semiconductors on the SOI platform for 2-4 mu m wavelength range integrated lasers and spectrometers, as well as tunable filters implemented on the Ge-on-SOI platform beyond 4 mu m