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In this work, high performance GeSn photoconductor and light emitting diodes (LED) have been demonstrated. For the photoconductor, the high responsivity was achieved due to high photoconductive gain, which is attributed to the novel optical and electrical design. The longwave cutoff at 2.4 μm was also observed at room temperature. For LED, temperature-dependent study was conducted. The electroluminescence (EL) spectra at different temperatures were obtained and EL peak shift was observed. Moreover, the emission power at different temperatures was measured. High power emission at 2.1 μm was achieved.

This paper reviews the invention, design and theoretical simulation of 2 x 2 and 1 x 4 optical routing switches. Insertion loss and crosstalk performance in the 1.55 to 3.0 μm wavelength range are predicted. The electrically actuated optical layer is a thin film of Ge2Sb2Te5 or GeTe or GeSe whose thickness is in the 10 to 100-nm range. This film was embedded at the centerline of an SOI, SON, or GeOI channel waveguide structure for MZI and directional-coupler switching Alternatively, to switch free-space light beams, Ge prisms sandwiching the film were employed. Devices are self-sustaining in each of their two states. Experiments are needed to confirm assumptions made in the theory about voltage requirements, speed, PCM index, and manufacturing techniques.

Theoretical modeling and numerical simulation have been performed at λ=2100 nm on silicon-on-insulator channel-waveguide directional couplers in which the outer two Si waveguides are passive and the central waveguide(s) are electro-optical (EO) "islands." The EO channel(s) utilize a 10 nm layer of Ge2Sb2Te5 phase-change-material sited at midlevel of a doped Si channel. A voltage-driven phase change produces a large change in the effective index of the TE(o) and TM(o) modes, thereby inducing crossbar 2×2 switching. A mode-matching method is employed to estimate EO switching performance in the limit of strong interguide coupling. Low-loss switching is predicted for cross-to-bar and bar-to-cross coupling lengths. These "self-holding" switches had active lengths of 500-1000 μm, which are shorter than those in couplers relying upon free-carrier injection. The four-waveguide devices had lower cross talk but higher loss than the three-waveguide devices. For the crystalline phase we sometimes used an active length that was smaller than that for the amorphous phase.

Characterization of GeSn edge-emitting LEDs has been conducted with Sn compositions up to 8%. Room temperature electroluminescence spectra and emission power were measured. A peak power of 50 mW was achieved with an 8%-Sn device.

A novel design of a two-bus coupled-rings 2 × 2 switch with inter-ring coupling enabled by a three-waveguide (3w) directional coupler is proposed. The device is analyzed using a theoretical model based on coupled mode theory and optical transfer formulae. We show that injected free-carriers tuning of the central waveguide in the 3w coupler affects only the bonding resonance mode while the other anti-bonding mode is transparent. This feature can be used to perform selective optical switching, and a numerical design example is given on the silicon photonics platform. The selective switch can be employed in a two-color duplex bidirectional communication system which conveniently separates the simultaneous transmitted and received signals in a single fiber-optic waveguide.

Platinum germanides (PtGe) were investigated for infrared plasmonic applications. Layers of Pt and Ge were deposited and annealed. X-ray diffraction identified PtGe(2) and Pt(2)Ge(3) phases, and x-ray photo-electron spectroscopy determined vertical atomic composition profiles for the films. Complex permittivity spectra were measured by ellipsometry over the 2 to 15 μm wavelength range. Surface plasmon polariton (SPP) characteristics such as propagation length and field penetration depth were calculated. Photon-to-SPP couplers in the form of 1D lamellar gratings were fabricated and characterized in the range 9 - 10.5 μm via wavelength-dependent specular reflection spectra for multiple angles of incidence. The observed resonances compare well with calculated spectra for SPP excitation on PtGe(2). Platinum germanides are CMOS compatible and may serve as SPP hosts for on-chip mid-IR plasmonic components with tighter field confinement than noble-metal hosts.

New device designs are proposed and theoretical simulations are performed on electro-optical routing switches in which light beams enter and exit the device either from free space or from lensed fibers. The active medium is a ~100 nm layer of phase change material (Ge(2)Sb(2)Te(5) or GeTe) that is electrically "triggered" to change its phase, giving "self-holding" behavior in each of two phases. Electrical current is supplied to that film by a pair of transparent highly doped conducting Ge prisms on both sides of the layer. For S-polarized light incident at ~80° on the film, a three-layer Fabry-Perot analysis, including dielectric loss, predicts good 1 x 2 and 2 x 2 switch performance at infrared wavelengths of 1.55, 2.1 and 3.0 μm, although the performance at 1.55 μm is degraded by material loss and prism mismatch. Proposals for in-plane and volumetric 1 x 4 and 4 x 4 switches are also presented. An unpolarized 1 x 2 switch projects good performance at mid infrared.

Ge 1-x Sn x /Ge thin films and Ge/Ge 1-x Sn x /Ge n-i-p double heterostructure (DHS) have been grown using commercially available reduced pressure chemical vapor deposition (RPCVD) reactor. The Sn compositional material and optical characteristics have been investigated. A direct bandgap GeSn material has been identified with Sn composition of 10%. The GeSn DHS samples were fabricated into LED devices. Room temperature electroluminescence spectra were studied. A maximum emission power of 28mW was obtained with 10% Sn LED under the injection current density of 800 A/cm 2 .

Si based Ge1-xSnx photoconductors, with Sn incorporation of 0.9, 3.2, and 7%, were fabricated using a CMOS-compatible process. Temperature dependent study was conducted from 300 to 77 K. The first generation device (standard photoconductor, PD) shows long wavelength cut-off beyond 2.1 μm for 7%-Sn devices at room temperature. The peak responsivity and D* of the 7% Sn device at 1.55 μm were obtained at 77K as 0.08 A/W and 1×109 cm*Hz1/2*W-1, respectively. Improved responsivity and specific detectivity (D*) were observed on second generation devices by a newly designed electrode structure (photoconductor with interdigitated electrodes, IEPD). The enhancement factor of responsivity was up to 15 at 77 K.

The pace of the development of silicon photonics has quickened since 2004 due to investment by industry and government. Commercial state-of-the-art CMOS silicon-on-insulator (SOI) foundries are now being utilized in a crucial test of 1.55-mum monolithic optoelectronic (OE) integration, a test sponsored by the Defense Advanced Research Projects Agency (DARPA). The preliminary results indicate that the silicon photonics are truly CMOS compatible. RD however, lasing has not yet been attained. The new paradigm for the Si-based photonic and optoelectric integrated circuits is that these chip-scale networks, when suitably designed, will operate at a wavelength anywhere within the broad spectral range of 1.2-100 mum, with cryocooling needed in some cases

We propose that the operational wavelength of waveguided Si-based photonic integrated circuits and optoelectronic integrated circuits can be extended beyond the 1.55 µ mt elecom range into the wide infrared from 1.55 to 100 µm. The Si rib-membrane waveguide offers low-loss transmission from 1.2 t o6 µ ma nd from 2 4t o 100µm. This waveguide, which is compatible with Si microelectronics manufacturing, is constructed from silicon-on-insulator by etching away the oxide locally beneath the rib. Alternatively, low-loss waveguiding from 1.9 to 14.7 µ mi s assured by employing a crystal Ge rib grown directly upon the Si substrate. The Si-based hollow-core waveguide is an excellent device that minimizes loss due to silicon’s 6–24 µ mm ulti-phonon absorption. Here the rectangular air-filled core is surrounded by SiGe/Si multi-layer anti-resonant or Bragg claddings. The hollow channel offers less than 1. 7d B cm −1 loss from 1.2 to 100 µm.

Using two-dimensional (2-D) scattering matrix theory, the switching behavior of inplane waveguided 2 /spl times/ 2 resonant optical switches in silicon-on-insulator was analyzed at the 1.33, 1.55, and 10.6 /spl mu/m wavelengths. The switch consisted of two straight bus waveguides coupled independently and laterally to a pair of microring resonators. Switching actuated by a /spl Delta/n + i/spl Delta//spl kappa/~ complex index perturbation of the rings was investigated. The switching effects discussed include the free-carrier-plasma dispersion, Franz-Keldysh, quantum-confined Stark, Kerr, and thermooptic effects. Each effect has its /spl Delta//spl kappa/~//spl Delta/n signature. For waveguides /spl les/0.3/spl lambda/ wide, an optimum switch design was determined in the weak coupling regime. Complete switching was found for /spl Delta/n/spl sim/2/spl times/10/sup -3/, together with significant modulation for /spl Delta/n in the 10/sup -4/ range.

We propose the idea of developing THz quantum cascade lasers (QCLs) with GaN-based quantum well (QW) structures with significant advantages over the currently demonstrated THz lasers in the GaAs-based material system. While the ultrafast longitudinal optical (LO) phonon scattering in AlGaN/GaN QWs can be used for the rapid depopulation of the lower laser state, the large LO-phonon energy (∼90 meV) can effectively reduce the thermal population of the lasing states at higher temperatures. Our analysis of one particular structure has shown that a relatively low threshold current density of 832 A/cm2 can provide a threshold optical gain of 50/cm at room temperature. We have also found that the characteristic temperature in this structure is as high as 136 K.

We report a theoretical investigation on the electrical properties of a Sn-based group-IV structure for a resonant tunneling diode (RTD). The analysis on the composition-dependent strain, energy profile, and current-voltage characteristic of a double-barrier heterostructure shows that the peak current density and peak-to-valley ratio are enhanced with a moderated tensile strain in the barrier layer, providing an alternative approach for group-IV RTDs.

A systematic design of a GaN/AlGaN active region for a three-level intersubband laser emitting in the near-infrared is presented. The proposed system is based on a double coupled quantum well structure with the laser level energy separation corresponding to 1.55 µm (ΔE32~800 meV), a wavelength important for optical communications. The lower laser level depopulates mostly via longitudinal optical phonon resonance, requiring ΔE21~90 meV. The model for scattering rate calculations, including many-body carrier screening effects, was first tested by comparison with recent experimental measurements in GaN/AlGaN quantum wells, and a very good agreement was obtained. It was then employed to calculate the gain coefficient, a commonly used figure of merit for three level laser systems, and this in turn allowed the optimal structural parameters of GaN/AlGaN quantum well to be found.

Asymmetric rolling, in which the circumferential velocities of the upper and lower rolls are different, can give rise to intense plastic shear strains and in turn shear deformation textures through the sheet thickness. The ideal shear deformation texture of fcc metals can be approximated by the // ND and {001} orientations, among which the former improves the deep drawability. The ideal shear deformation texture for bcc metals can be approximated by the Goss {110} and {112} orientations, among which the former improves the magnetic permeability along the directions and is the prime orientation in grain oriented silicon steels. The intense shear strains can result in the grain refinement and hence improve echanical properties. Steel sheets, especially ferritic stainless steel sheets, and luminum alloy sheets may exhibit an undesirable surface roughening known as ridging or roping, when elongated along RD and TD, respectively. The ridging or roping is caused by differently oriented colonies, which are resulted from the oriented columnar structure in ingots or billets, especially for ferritic stainless steels, that is not easily destroyed by the conventional rolling. The breakdown of columnar structure and the grain refinement can be achieved by asymmetric rolling, resulting in a decrease in the ridging problem.

The prospects and advantages of silicon germanium quantum cascade lasers are discussed, from both physical and technological perspectives. A range of Si/SiGe intersubband laser configurations are discussed, for both edge and surface emission. Recent experimental activity on mid- and far-infrared devices is reviewed, and the value of detailed theoretical tools for heterostructure design is highlighted. Steps towards silicon optoelectronic integration are also considered.

Design and simulation results are presented for an on-chip 2×2 Mach-Zehnder-based optical switch where each arm of the interferometer is composed of a coupled-resonator optical waveguide. The individual resonators are one-dimensional photonic crystal nanobeam cavities, and switching occurs through thermally induced changes in the refractive index of the silicon structure using integrated heating pads. The performance of the coupled-resonator device is directly compared to its single resonator counterpart, and significant improvement is found in the bar-state CT metric.

© 2014 Optical Society of America. In a theoretical design study, we propose buried waveguides made of germanium or alloys of germanium and other group-IV elements as a CMOS-compatible platform for robust, high-gain stimulated Brillouin scattering (SBS) applications in the mid-infrared regime. To this end, we present numerical calculations for backward-SBS at 4mm in germanium waveguides that are buried in silicon nitride. Due to the strong photoelastic anisotropy of germanium, we investigate two different orientations of the germanium crystal with respect to the waveguide's propagation direction and find considerable differences. The acoustic wave equation is solved including crystal anisotropy; acoustic losses are computed from the acoustic mode patterns and previously published material parameters.

In this paper we present a detailed theoretical investigation of integrated racetrack Raman lasers based on the germanium material system operating in the mid-infrared beyond the germanium two-photon absorption cut-off wavelength of 3.17 μm. The effective Raman gain has been estimated in waveguides based on germanium-on-silicon, germanium-on-SOI and germanium-on-Si3N4 technology platforms as a function of their crystallographic orientations. Furthermore, general design guidelines have been determined by means of a comparative analysis of Raman laser performance, i.e. the threshold power, polarization and directionality of the excited Stokes signals as a function of racetrack cavity length and directional-coupler dimensions. Finally, the emitted Raman laser power has been evaluated as a function of overall propagation losses and operative wavelengths up to 3.8 μm, while the time dynamics of Raman lasers has been simulated assuming continuous and pulse waves as input pump signals.

The Ge 0.9 Sn 0.1 photoconductor was fabricated with interdigitated structures on Si using a CMOS-compatible process. Temperature-dependent responsivity and specific detectivity were measured. The peak responsivity of 2.85A/W at 77K was achieved due to enhanced photoconductive gain.

The influence of high-order susceptibilities on the supercontinuum generation process in germanium-on-silicon waveguides has been investigated in detail in the midinfrared. The frequency dispersion of both the three-photon absorption coefficient and the real part of the fifth-order susceptibility has been investigated in order to develop a self-consistent modeling based upon a generalized nonlinear Schrodinger equation. Numerical results demonstrate that germanium-on-silicon waveguides can be used to induce supercontinuum generation over 1.34-μm-wide bandwidth with 200-fs input pulses pumped at a wavelength of 4 μm with peak pump powers of 89 W and waveguide lengths of 4.6 mm. The soliton fission process has also been observed as it is the main mechanism behind the supercontinuum generation.

At wavelengths of 1.55 to 3.0 μm, theoretical simulations were made of electro-optical 2 x 2 switching utilizing a thin-film of Ge2Sb2Te5 or GeTe or GeSe that offers two voltage-triggered self-holding optical states. Low loss and low crosstalk were predicted but experiments are needed to confirm the theory.

Here we demonstrate a reconfigurable electro-optical directed-logic circuit based on a 4-fold array of switches. We showed that this circuit can be reconfigured to perform arbitrary two-input logic functions with speed up to 3 Gb/s.

This work is motivated by the desire to extend the operating wavelength of contemporary quantum well infrared photodetectors from the mid- ( 20μm) or terahertz region of the electromagnetic spectrum without recourse to liquid helium temperatures. This apparently simple objective hides many challenges which stem from the parasitic current that flows even in the absence of any illumination—the so-called dark current.

A SiGeSn/GeSn/SiGeSn single quantum well structure featuring type-I band alignment was comprehensively characterized. Three pump lasers with different penetration depths and photon energies were used to pinpoint the optical transition characteristics of the sample. The carrier generation, redistribution, and recombination under each pumping condition were analyzed in detail. By comparing the temperature-dependent photoluminescence spectra of the GeSn quantum well with that of SiGeSn and GeSn thin film samples possessing similar Si and Sn compositions, the optical transition mechanism was clearly identified.

Ultrafast Kerr effect switching in near-infrared two-photon absorption (TPA)-free and free-carrier-absorption (FCA)-free nonstoichiometric silicon carbide (SixC1−x) microring waveguides is performed and investigated. With pulsed return-to-zero on–off-keying (PRZ-OOK) stream for the Si-rich SixC1−x-based all-optical switches, the inversely modulated probe reveals an asymmetric bit shape data extinction ratio (ER) of only 8.7 dB owing to the TPA + FCA effect. By eliminating the FCA effects in nearly stoichiometric SixC1−x microring waveguide, the high-speed wavelength conversion of a data stream with an ER of 14 dB can be observed when coinciding the probe wavelength with the transmission dip. Slightly deviating the probe wavelength from the transmission dip, most probe power still remains in bus waveguide to cause a strong FCA effect to degrade the ER down to 7.4 dB. A symmetrically converted and inverted data stream with high on/off extinction can be observed in the C-rich SixC1−x-based microring waveguide with completely suppressed trailing-edge response. To further approach the upper limitation on bandwidth, the wavelength-converted and sign-reversible PRZ-OOK data switching at a bit rate up to 12 Gbit s−1 can be obtained with similar ER of better than 20 dB, as contributed mainly by the enhanced Kerr nonlinearity in the C-rich SixC1−x.

We propose and experimentally demonstrate a 2×2 thermo-optic (TO) crossbar switch implemented by dual photonic crystal nanobeam (PCN) cavities within a silicon-on-insulator (SOI) platform. By thermally tuning the refractive index of silicon, the resonance wavelength of the PCN cavities can be red-shifted. With the help of the ultrasmall mode volumes of the PCN cavities, only ∼0.16 mW power is needed to change the switching state. With a spectral passband of 0.09 nm at the 1583.75 nm operation wavelength, the insertion loss (IL) and crosstalk (CT) performances were measured as IL(bar)=−0.2 dB, CT(bar)=−15 dB, IL(cross)=−1.5 dB, and CT(cross)=−15 dB. Furthermore, the thermal tuning efficiency of the fabricated device is as high as 1.23 nm/mW.

The GeSn direct gap material system, with Si complementary-metal-oxide semiconductor (CMOS) compatibility, presents a promising solution for direct incorporation of focal plane arrays with short wave infrared detection on Si. A temperature dependence study of GeSn photoconductors with 0.9, 3.2, and 7.0% Sn was conducted using both electrical and optical characterizations from 300 to 77 K. The GeSn layers were grown on Si substrates using a commercially available chemical vapor deposition reactor in a Si CMOS compatible process. Carrier activation energies due to ionization and trap states are extracted from the temperature dependent dark I-V characteristics. The temperature dependent spectral response of each photoconductor was measured, and a maximum long wavelength response to 2.1 μm was observed for the 7.0% Sn sample. The DC responsivity measured at 1.55 μm showed around two orders of magnitude improvement at reduced temperatures for all samples compared to room temperature measurements. The noise current and temperature dependent specific detectivity (D*) were also measured for each sample at 1.55 μm, and a maximum D* value of 1 × 10(9) cm·√Hz/W was observed at 77 K.

GeSn films were annealed in cycles of 30 s at 450 and 500 C. The annealing temperature and number of cycles for material quality enhancement and relaxation depends upon Sn mole fraction and film thickness.

The spectral response and responsivity of a GeSn photoconductor were measured from 300 to 77 K. The maximum responsivity of 0.06 A/W was measured at 1550 nm for 10 volts bias at 140 K.

The wavelength range that extends from 1550 to 5000 nm is a new regime of operation for Si-based photonic and opto-electronic integrated circuits. To actualize the new chips, heterostructure active devices employing the ternary SiGeSn alloy are proposed in this paper. Foundry-based monolithic integration is described. Opportunities and challenges abound in creating laser diodes, optical amplifiers, light-emitting diodes, photodetectors, modulators, switches and a host of high-performance passive infrared waveguided components.

An analysis, by a carrier scattering approach, of the thermionic emission contribution to the dark current is carried out in conventional bound-to-continuum quantum well infrared photodetectors (QWIPs). It is found that the thermionic emission increases with increasing temperature or when extending the detection wavelength from mid- to far-infrared. Considering p-type instead of n-type material, however, the increased effective mass decreases the thermionic emission. Designs for mid- and far-infrared p-type QWIPs based on the Si 1 − xGe x/Si system are discussed for both normal and non-normal incident geometries.

We have investigated a solid-state design advanced (see Soref et al. in SPIE Proceedings, vol.3795, p.516, 1999) to achieve a terahertz-amplification-by-the-stimulated-emission-of-radiation (TASER). The original design was based on light-to heavy-hole intersubband transitions in SiGe-Si heterostructures. This work adapts the design to electron intersubband transitions in the more readily available GaAs/Ga/sub 1-x/Al/sub x/As material system. It is found that the electric-field induced anti-crossings of the states, derived from the first excited state with the ground states of a superlattice in the Stark-ladder regime, offers the possibility of a population inversion and gain at room temperature.

Ingenious techniques are needed to extend group IV photonics from near-infrared to mid-infrared wavelengths. If achieved, the reward could be on-chip CMOS optoelectronic systems for use in spectroscopy, chemical and biological sensing, and free-space communications.

A superlattice consisting of periods of $90\AA{} {\mathrm{Si}}_{0.7}{\mathrm{Ge}}_{0.3}$ quantum wells and 50 \AA{} Si barriers on a $(100) {\mathrm{Si}}_{0.81}{\mathrm{Ge}}_{0.19}$ buffer is investigated for the purpose of designing Si-based terahertz intersubband lasers using the feature of inverted light-hole effective mass. It has been shown that the energy subband dispersion curve of this structure demonstrates a region of inverted light-hole effective mass. Since the energy separation between the two lowest subbands that are also of different type is below the optical phonon energy, acoustic phonon scattering is an important nonradiative process and is therefore studied. Our result indicates that the intersubband phonon scattering process is much weaker between different types of subband. For the particular structure of interest, this scattering rate is about 0.5/ns, corresponding to an intersubband lifetime of 2 ns, which is much longer than the typical lifetime of 1 ps when it is between subbands of the same kind.

High-speed 2 μm digital optical receivers are brought closer to reality by an extended-response foundry-made monolithic silicon-on-insulator avalanche photodiode.

Simulations of a room-temperature p-i-p coherently strained Si0.5Ge0.5/Si superlattice quantum-parallel laser diode have been made. Calculations have been made of the local-in-k-space population inversion between the nonparabolic heavy-hole valence minibands, HH2 and HH1. Lasing is at 5.4 μm and the optical dipole matrix element is 3.7 A. Analysis of radiative-and-phonon scattering between the “mixed” bands indicates a lifetime difference between the upper and lower states of 2.4 ps. At an injected current density of 5000 A/cm2, a laser gain of 134 cm−1 is calculated.

Silicon-based optoelectronics is a diversified technology that has grown steadily but not exponentially over the past decade. Some applications—such as smart-pixel signal processing and chip-to-chip optical interconnects—have enjoyed impressive growth, whereas other applications have remained quiescent. A few important applications such as optical diagnosis of leaky metal-oxide-semiconductor-field-effect-transistor circuits, have appeared suddenly. Over the years, research and development has unveiled some unique and significant aspects of Si-based optoelectronics. The main limitation of this technology is the lack of practical silicon light sources—Si lasers and efficient Si light-emitting devices (LEDs)—though investigators are “getting close” to the LED.Silicon-based optoelectronics refers to the integration of photonic and electronic components on a Si chip or wafer. The photonics adds value to the electronics, and the electronics offers low-cost mass-production benefits. The electronics includes complementary-metal-oxide semiconductors (CMOS), very large-scale integration (VLSI), bipolar CMOS, SiGe/Si heterojunction bipolar transistors, and heterostructure field-effect transistors. In this discussion, we will use a loose definition of optoelectronics that includes photonic and optoelectronic integrated circuits (PICs and OEICs), Si optical benches, and micro-optoelectromechanical (MOEM) platforms. Optoelectronic chips and platforms are subsystems of computer systems, communication networks, etc. Silicon substrates feature a superior native oxide, in addition to excellent thermal, mechanical, and economic properties. Silicon wafers “shine” as substrates for PICs and OEICs.

The critical design issues for unipolar silicon quantum-well intersubband lasers are investigated in this paper. Group IV lasing at near-infrared and middle-infrared wavelengths is analyzed for surface-emitting and edge-emitting geometries. Calculations show feasibility of SiGe/Si and SiGe/Si lasing. Silicon-on-insulator structures are proposed for index-guided lasers, vertical-cavity lasers and micro-cavity lasers

Thin film Ge1-xSnx photodetectors fabricated on Si using a CMOS compatible process had responsivities at 1.55 mm of 6.59, 1.49, 2.63, and 0.84 mA/W for 0.9, 2.57, 3.2, and 7.0 % Sn. Spectral response for a Ge0.93Sn0.07 photodetector had extended infrared response out to 2.2 mm.

We report on strong index modulation of ITO-hybrid-plasmon gate stacks at telecomm wavelengths verified by gated ellipsometry for the first time. Using these results we design a compact 3-waveguide electro-optic switch for photonic integration.

A lateral p-n junction nanobeam electro-optic modulator for the 8 micron regime is presented. Owing to a strong free-carrier absorption effect, an ultralow switching energy is achieved, while utilizing a small footprint, monolithic, and VLSI-compatible implementation.

Photoluminescence (PL) from Ge1-xSnx grown on Si by CVD was investigated for Sn composition of 0.9, 3.2, 6, and 7%, respectively. The direct and indirect band transitions were analyzed at different temperatures.

We design low-loss single-mode GeSn mid-infrared waveguides on group-IV substrates including Si substrates and Ge-on-SOI substrates. The waveguide geometries under single mode condition are optimized for different GeSn alloy compositions and polarizations.