InP-based Materials Research Articles

Enhanced Luminous Efficacy and Stability of InP/ZnSeS/ZnS Quantum Dot-Embedded SBA-15 Mesoporous Particles for White Light-Emitting Diodes.

Environmentally friendly quantum dots (QDs) of InP-based materials are widely investigated, but their reliability remains inadequate to realize their full potential and wide application. In this study, InP/ZnSeS/ZnS QDs (pristine QDs) were dispersed and embedded into Santa Barbara Amorphous-15 mesoporous particles (SBA-15 MPs) for the first time. A solvent-free method for preparing QD white light-emitting diodes (WLEDs) that is compatible with the WLED packaging process was developed. The photoluminescence (PL) spectrum of pristine QD powder exhibited cluster states and had huge redshift of approximately 23 nm. By comparison, the PL spectrum of the SBA-15 MP/QD hybrid powder had a slight redshift of approximately 8 nm, only because the pristine QDs were dispersed and embedded well in the SBA-15 MPs. The PL intensity of the SBA-15 MP/QD hybrid powder slightly decreased after heating and cooling compared with that of the pristine QDs. Moreover, the luminous efficacy of the SBA-15 MP/QD hybrid WLEDs was enhanced by approximately 14% compared with that of the pristine QD-WLEDs. Furthermore, reliability analysis revealed that the SBA-15 MPs could improve the stability of the pristine QDs on chips. Thus, these MPs promise good potential for applications in mini-LEDs in the future.

High optical gain in InP-based quantum-dot material monolithically grown on silicon emitting at telecom wavelengths

We describe the fabrication process and properties of an InP based quantum dot (QD) laser structure grown on a 5° off-cut silicon substrate. Several layers of QD-based dislocation filters embedded in GaAs and InP were used to minimize the defect density in the QD active region which comprised eight emitting dot layers. The structure was analyzed using high resolution transmission electron microscopy, atomic force microscopy and photoluminescence. The epitaxial stack was used to fabricate optical amplifiers which exhibit electroluminescence spectra that are typical of conventional InAs QD amplifiers grown on InP substrates. The amplifiers avail up to 20 dB of optical gain, which is equivalent to a modal gain of 46 cm−1.

AlGaInAs Multi-Quantum Well Lasers on Silicon-on-Insulator Photonic Integrated Circuits Based on InP-Seed-Bonding and Epitaxial Regrowth

The tremendous demand for low-cost, low-consumption and high-capacity optical transmitters in data centers challenges the current InP-photonics platform. The use of silicon (Si) photonics platform to fabricate photonic integrated circuits (PICs) is a promising approach for low-cost large-scale fabrication considering the CMOS-technology maturity and scalability. However, Si itself cannot provide an efficient emitting light source due to its indirect bandgap. Therefore, the integration of III-V semiconductors on Si wafers allows us to benefit from the III-V emitting properties combined with benefits offered by the Si photonics platform. Direct epitaxy of InP-based materials on 300 mm Si wafers is the most promising approach to reduce the costs. However, the differences between InP and Si in terms of lattice mismatch, thermal coefficients and polarity inducing defects are challenging issues to overcome. III-V/Si hetero-integration platform by wafer-bonding is the most mature integration scheme. However, no additional epitaxial regrowth steps are implemented after the bonding step. Considering the much larger epitaxial toolkit available in the conventional monolithic InP platform, where several epitaxial steps are often implemented, this represents a significant limitation. In this paper, we review an advanced integration scheme of AlGaInAs-based laser sources on Si wafers by bonding a thin InP seed on which further regrowth steps are implemented. A 3 µm-thick AlGaInAs-based MutiQuantum Wells (MQW) laser structure was grown onto on InP-SiO2/Si (InPoSi) wafer and compared to the same structure grown on InP wafer as a reference. The 400 ppm thermal strain on the structure grown on InPoSi, induced by the difference of coefficient of thermal expansion between InP and Si, was assessed at growth temperature. We also showed that this structure demonstrates laser performance similar to the ones obtained for the same structure grown on InP. Therefore, no material degradation was observed in spite of the thermal strain. Then, we developed the Selective Area Growth (SAG) technique to grow multi-wavelength laser sources from a single growth step on InPoSi. A 155 nm-wide spectral range from 1515 nm to 1670 nm was achieved. Furthermore, an AlGaInAs MQW-based laser source was successfully grown on InP-SOI wafers and efficiently coupled to Si-photonic DBR cavities. Altogether, the regrowth on InP-SOI wafers holds great promises to combine the best from the III-V monolithic platform combined with the possibilities offered by the Si photonics circuitry via efficient light-coupling.

Low-Threshold, High-Power On-Chip Tunable III-V/Si Lasers with Integrated Semiconductor Optical Amplifiers

Heterogeneously integrated III-V/Si lasers and semiconductor optical amplifiers (SOAs) are key devices for integrated photonics applications requiring miniaturized on-chip light sources, such as in optical communications, sensing, or spectroscopy. In this work, we present a widely tunable laser co-integrated with a semiconductor optical amplifier in a heterogeneous platform that combines AlGaInAs multiple quantum wells (MQWs) and InP-based materials with silicon-on-insulator (SOI) wafers containing photonic integrated circuits. The co-integrated device is compact, has a total device footprint of 0.5 mm2, a lasing current threshold of 10 mA, a selectable wavelength tuning range of 50 nm centered at λ = 1549 nm, a fiber-coupled output power of 10 mW, and a laser linewidth of ν = 259 KHz. The SOA provides an on-chip gain of 18 dB/mm. The total power consumption of the co-integrated devices remains below 0.5 W even for the most power demanding lasing wavelengths. Apart from the above-mentioned applications, the co-integration of compact widely tunable III-V/Si lasers with on-chip SOAs provides a step forward towards the development of highly efficient, portable, and low power systems for wavelength division multiplexed passive optical networks (WDM-PONs).

Dilute nitride resonant-cavity light emitting diode

Resonant cavity LEDs (RCLEDs) are a viable and low-cost alternative light source to lasers for optical communication systems in the 1.3 µm O-band. Most work in this area has been conducted on InP-based material, which is inherently costly, devices often require cooling and the refractive index contrast for constructing mirrors is low. Here, we demonstrate a high-performance GaAs-based RCLED using a dilute nitride GaInNAs active layer emitting in the 1.3 μm wavelength window. While previous 1.3 µm RCLEDs have used metallic mirrors on the back of the device, we exploit the high refractive index contrast of the GaAs/AlAs system to place Distributed Bragg mirrors on both sides of the active layer and achieve superior performance. The external quantum efficiency of the devices is 20% and the full width at half maximum of the emission spectrum is 5.2 nm at room temperature, into a narrow angular cone. The emission power from an 88 μm diameter aperture is 0.5 mW, which, together with the narrow spectral linewidth, makes the device suitable for deployment in a coarse Wavelength Division Multiplexing (WDM) communications system.

Wavelength Extended InGaAsBi Detectors with Temperature-Insensitive Cutoff Wavelength**Supported by the National Key Research and Development Program of China under Grant No 2016YFB0402400, the National Basic Research Program of China under Grant No 2014CB643900, the National Natural Science Foundation of China under Grant Nos 61775228, 61605232, 61675225 and 61334004, and the Shanghai Rising-Star Program under Grant No 17QA1404900.

We demonstrate a wavelength extended InGaAsBi short-wave infrared photodetector on an InP substrate with the 50% cutoff wavelength up to 2.63 μm at room temperature. The moderate growth temperature is applied to balance the Bi incorporation and material quality. Photoluminescence and x-ray diffraction reciprocal space mapping measurements reveal the contents of bismuth and indium in InGaAsBi to be about 2.7% and 76%, respectively. The InGaAsBi detector shows the temperature-insensitive cutoff wavelength with a low coefficient of about 0.96 nm/K. The demonstration indicates the InP-based InGaAsBi material is a promising candidate for wavelength extended short-wave infrared detectors working.

(Invited) Heterogeneous Photonic Integration by Direct Wafer Bonding

The silicon photonics platform has emerged as a promising integration technique for use in many applications, particularly datacenter communications, which is expected to produce demand for large numbers of low cost photonic integrated circuits (PICs). Silicon-based PICs are almost universally based on silicon-on-insulator (SOI) wafers, which are enabled by wafer bonding technology. Silicon (Si) is useful as a waveguide material due to its high index contrast, low intrinsic absorption, and mature manufacturing infrastructure. However, it does not strongly interact with light in wavelength ranges of interest for data transmission. Heterogeneous integration of InP-based materials with Si using wafer bonding technology is able to overcome this limitation and has allowed the realization of a wide range of photonic devices on Si1. Beyond integration of InP with Si, wafer bonding enables complex vertical integration with of a wide variety of materials, such as silicon nitride (Si3N4) ultra-low loss waveguides, and magnetic and nonlinear materials. A crystalline Si layer transferred to an ultra-low loss Si3N4 waveguide wafer by bonding allows for integration of highly confined Si photonic waveguide with low-loss passive components in Si3N4. Any device that can be realized on an SOI wafer can be integrated with the Si3N4 waveguide. Multiple die bonding of InP chips on the Si layer can add lasers, amplifiers, modulators, and photodetectors to the circuit. Lateral tapers of the waveguides allows coupling between the layers with loss below 0.5 dB. This technology was used to combine a Si3N4 arrayed waveguide grating (AWG) wavelength multiplexer with high-speed 50 Gb/s heterogeneous Si/InP photodetectors to form a 400 Gb/s wavelength division multiplexing (WDM) receiver2. A cross section of the photodetector is shown in Figure 1. Bonding technology can allow the introduction of additional circuit functions that are unavailable using common semiconductor materials. One such device is an optical isolator, which allows light to experience loss that is dependent on the direction of optical propagation. This optical nonreciprocity can be achieved by bonding a magneto-optic material such as cerium substituted yttrium iron garnet (Ce:YIG) on Si waveguides, and applying a magnetic field through the material. Using this phenomenon, it is possible to fabricate optical isolators as well as circulators for use in optical sensors, amplifiers, and WDM systems. Our design consists of a Si microring with a bonded Ce:YIG die on top, shown schematically in Figure 2. A metallic microstrip is deposited on the backside of the bonded die following substrate removal. By applying a current through this microstrip, we generate a magnetic field, which causes a resonance split between the forward and backwards propagating light. Thus, optical isolators with up to 32 dB of isolation have been demonstrated3. Lithium niobate (LN) is a material of paramount importance for nonlinear optics, thanks to its large nonlinear coefficient and broad transparent window (0.4-5.0 µm)4. It has attracted attention for use in PICs, because the compact scale of integrated waveguides results in high photon densities that effectively enhance nonlinear interaction. Recently, the LN-on-insulator (LNOI) technology has been successfully demonstrated by ion injection and heterogeneous bonding. This allows the implementation of LN thin films with submicron thickness on various material platforms5. We present here a quasi-phase matched, ultra-low-loss S3N4-LN platform, which reduces the loss of integrated LN waveguides down to a value comparable with best results of bulk LN waveguides 6 (Figure 3). Bonding of LN to silicon is also possible, allowing integration of LN-based devices with SOI photonics. Wafer bonding technology allows the realization of complex and highly integrated photonic devices. The ability to combine multiple materials such as multiple-die bonding for integration of lasers, modulators, and detectors enables PICs with a wide variety of functions. Vertical integration through bonding of high-quality thin films, such as silicon nitride, lithium niobate, crystalline silicon, and thermal silicon dioxide can be used to construct integrated waveguides with useful properties and high performance. 1. M. J. R. Heck et al., IEEE J. Sel. Top. Quantum Electron. 19, 6100117 (2013). 2. M. Piels, J. F. Bauters, M. L. Davenport, M. J. R. Heck, and J. E. Bowers, J. Light. Technol. 32, 817–823 (2014). 3. D. Huang et al., Optical Fiber Communications (2016). 4. G. D. Boyd, R. C. Miller, K. Nassau, W. L. Bond, and A. Savage, Appl. Phys. Lett. 5, 234–236 (1964). 5. L. Chen, Q. Xu, M. G. Wood, and R. M. Reano, Optica 1, 112 (2014). 6. K. R. Parameswaran et al., Opt. Lett. 27, 179–181 (2002). Figure 1

Hybrid III-V/SOI resonant cavity enhanced photodetector.

A hybrid III-V/SOI resonant-cavity-enhanced photodetector (RCE-PD) structure comprising a high-contrast grating (HCG) reflector, a hybrid grating (HG) reflector, and an air cavity between them, has been proposed and investigated. In the proposed structure, a light absorbing material is integrated as part of the HG reflector, enabling a very compact vertical cavity. Numerical investigations show that a quantum efficiency close to 100 % and a detection linewidth of about 1 nm can be achieved, which are desirable for wavelength division multiplexing applications. Based on these results, a hybrid RCE-PD sample has been fabricated by heterogeneously integrating an InP-based material onto a silicon-on-insulator wafer and has been characterized, which shows a clear enhancement in photo-current at the designed wavelength. This indicates that the HG reflector provides a field enhancement sufficient for RCE-PD operation. In addition, a capability of feasibly selecting the detection wavelength during fabrication as well as a possibility of realizing silicon-integrated bidirectional transceivers are discussed.

Single-photon emission of InAs/InP quantum dashes at 1.55 μm and temperatures up to 80 K

We report on single photon emission from a self-assembled InAs/InGaAlAs/InP quantum dash emitting at 1.55 μm at the elevated temperatures. The photon auto-correlation histograms of the emission from a charged exciton indicate clear antibunching dips with as-measured g(2)(0) values significantly below 0.5 recorded at temperatures up to 80 K. It proves that the charged exciton complex in a single quantum dash of the mature InP-based material system can act as a true single photon source up to at least liquid nitrogen temperature. This demonstrates the huge potential of InAs on InP nanostructures as the non-classical light emitters for long-distance fiber-based secure communication technologies.

Inside view

Gallium arsenide finds use in a great number of electronics applications, and one of these is antireflection components in optoelectronic devices. Professor Douglas Hall of the University Of Notre Dame in the US tells us a bit more about his group's latest work in this field. Yuan Tian, Jinyang Li, and Doug Hall outside the Notre Dame Nanofabrication Facility, where the processing and some of the characterisation work was performed Gallium arsenide (GaAs) is widely used for optoelectronic devices such as photodetectors, solar cells, and red through amber LEDs. Uncoated GaAs has a reflectance of ∼33-47% across the visible spectrum. All of these devices can benefit from an antireflection layer on the surface to improve light collection or extraction efficiency. Many researchers (dating back to Henry Minden at General Electric in 1962) have tried a wide variety of methods to form a useful, insulating dielectric layer on the III-V compound semiconductor GaAs, akin to silicon dioxide grown on silicon. However, similar thermal oxidation processes do not readily work for GaAs because the material decomposes (i.e., Ga and As atoms “dissociate”) at the temperatures over 800°C typically used with silicon. We have recently discovered a means to directly oxidise GaAs at the relatively low temperature of 420°C. In this Letter, we show that the GaAs oxide films formed have a suitable refractive index and sufficiently smooth interfaces to form a useful antireflection (AR) layer on GaAs. The thermal oxidation methods previously reported for GaAs have typically used temperatures in the 510-700°C range and often resulted in low quality films with poor adhesion and rough surfaces and interfaces due to extensive pitting caused by dissociation. Most prior work doesn't report surface or interface roughness for these reasons. To form a high-performance AR layer based on thin-film interference effects, very smooth top and bottom oxide interfaces are absolutely essential so that two highly specular reflections are able to interfere destructively (when a relative phase shift of 180° is obtained for a given thickness and refractive index). In addition to our reported atomic force microscopy measurements of roughness, the close match between modelled and measured reflectance for the GaAs oxide AR layers realised in this work demonstrates the excellent interface quality of the oxides obtained through our process. When conventional wet-thermal oxidation of aluminum gallium arsenide (AlGaAs) was discovered by John Dallesasse et al. at the University of Illinois in 1990, it was found to be widely applicable only to alloys containing higher Al/Ga ratios, given the much greater chemical reactivity of Al. Around 2001, we found that oxidation rates of lower Al content alloys could be significantly enhanced (an order of magnitude or more) by mixing dilute amounts of oxygen into the water vapor process gas. In subsequent studies, we have learned that even Al-free alloys like GaAs and InGaAs can be oxidised, but the gas mixture must be carefully optimised and precisely controlled within a quite narrow “sweet spot”, a range of ∼0.1-0.2% oxygen flow rates relative to our nitrogen carrier gas. If too high or too low, or if small amounts of air leak into the system, surface quality and uniformity degrade, or no oxide grows at all. Even in 1962, Minden mixed water vapor with oxygen in the first reported study on GaAs oxidation, but concluded that it had no effect for temperatures under 800°C! This indicates that finding the proper O2/H2O ratio is critically important, and not just any mixture of these gases will do. We have elucidated the “why and how” details of the chemistry involved in some of our group's earlier papers on this subject. Optical microscope image of three oxidised GaAs samples on top of an unoxidised GaAs wafer We have recently been working to further enhance several aspects of the process control in our III-V compound semiconductor oxidation furnace, especially to more precisely regulate and monitor the optimal mixed gas ratios. Our wider research interests include applications of these native oxides to improve optical waveguides for semiconductor lasers and photonic integration, and we are currently actively exploring the extension of our process to telecommunications-wavelength InP-based materials and devices. As much as oxides of high-Al content alloys have found very widespread use for current apertures in commercial vertical cavity surface emitting lasers over the past 10-20 years, we would like to see the enhanced performance of other optoelectronic and photonic devices through the incorporation of oxidised low-Al content, Al-free, and InP-based alloys enabled by the mixed-gas oxidation process demonstrated in this work.

Single photon emission at 1.55 μm from charged and neutral exciton confined in a single quantum dash

We investigate charged and neutral exciton complexes confined in a single self-assembled InAs/InGaAlAs/InP quantum dash emitting at 1.55 μm. The emission characteristics have been probed by measuring high-spatial-resolution polarization-resolved photoluminescence and cross-correlations of photon emission statistics at T = 5 K. The photon auto-correlation histogram of the emission from both the neutral and charged exciton indicates a clear antibunching dip with as-measured g(2)(0) values of 0.18 and 0.31, respectively. It proves that these exciton complexes confined in single quantum dashes of InP-based material system can act as true single photon emitters being compatible with standard long-distance fiber communication technology.

A 474 GHz HBV Frequency Quintupler Integrated on a 20 <formula formulatype="inline"><tex Notation="TeX">$\mu{\hbox{m}}$</tex> </formula> Thick Silicon Substrate

We present a silicon integrated Heterostructure Barrier Varactor (HBV) frequency quintupler ( $\times$ 5) operating between 440 GHz and 490 GHz. By epitaxial transfer of InP-based HBV material structure onto silicon-on-insulator (SOI), a uniform and accurate thickness (20 $\mu{\hbox{m}}$ ) of the frequency quintupler chip is achieved. In a single stage this device delivers 2.8 mW of output power at 474 GHz, when pumped with 400 mW at 94.75 GHz, corresponding to conversion efficiency of 0.75%. The present device exhibits a 3-dB bandwidth of 4%.

InGaAs/GaAsSb/InP terahertz quantum cascade lasers

The development of In0.53Ga0.47As/GaAs0.51Sb0.49 terahertz quantum cascade lasers is reviewed, starting with the first demonstration, through growth direction dependent performance issues, to high performance devices. This InP-based material system is an attractive alternative to the almost exclusively used GaAs/AlxGa1-xAs. Devices achieve maximum operating temperatures of 142 K and exhibit broadband lasing over a range of 660 GHz. A special focus has to be put on the growth direction related interface asymmetry for this material system. Symmetric active region designs are an elegant technique to investigate such asymmetries. A significant impact on the device performance is observed and attributed to interface roughness scattering.

A Comparative Study of Fabrication of Long Wavelength Diode Lasers Using CCl<sub>2</sub>F<sub>2</sub>/O<sub>2</sub> and H<sub>2</sub>/CH<sub>4</sub>

We report comparatively on fabrication of two-section ridge-waveguide tapered 3 quantum well (QW) InGaAsP/InP (1300 nm) and 5 QW AlGaInAs/InP (1550 nm) diode lasers. Gas mixtures of CCl2F2/O2 and H2/CH4 were used to form ridge-waveguide on the lasers with InP-based material structures. As known, chlorine- and hydro-carbon based gases are used to fabricate ridge-waveguide structures. Here, we show the difference between the structures obtained by using the both gas mixtures in which surface and sidewall structures as well as performance of the lasers were analysed using scanning electron microscopy. It is demonstrated that gas mixtures of CCl2F2/O2 highly deteriorated the etched structures although different flow rates, rf powers and base pressures were tried. We also show that the structures etched with H2/CH4 gas mixtures produced much better results that led to the successful fabrication of two-section devices with ridge-waveguide. The lasers fabricated using H2/CH4 were characterized using output power-current (P-I) and spectral results.

Room temperature continuous wave operation of λ ∼ 3–3.2 μm quantum cascade lasers

We demonstrate quantum cascade lasers emitting at wavelengths of 3–3.2 μm in the InP-based material system. The laser core consists of GaInAs/AlInAs using strain balancing technique. In room temperature pulsed mode operation, threshold current densities of 1.66 kA/cm2 and 1.97 kA/cm2, and characteristic temperatures (T0) of 108 K and 102 K, are obtained for the devices emitting at 3.2 μm and 3 μm, respectively. Room temperature continuous wave operation is achieved at both wavelengths.

GaInAs/GaAsSb-based type-II micro-cavity LED with 2–3 μm light emission grown on InP substrate

In this paper we present the epitaxial growth and characterization of an InP-based micro-cavity light emitting diode (LED) with up to 3μm light emission by using GaInAs/GaAsSb-based type-II quantum wells. The LED was grown by LP-MOVPE and achieves emission from 2μm to 3μm at room-temperature. Furthermore a second LED with centered emission at 2.8μm has been realized. Hence, the achievable long-wavelength electroluminescence emission with InP-based materials has been extended up to 3μm.

Room Temperature Optically Pumped 2.56-$\mu{\rm m}$ Lasers With “W” Type InGaAs/GaAsSb Quantum Wells on InP Substrates

The optically pumped laser using InGaAs/GaAsSb W-type quantum wells is demonstrated with a threshold power density ~ 40 kW/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The L-L curve and the dramatic line width shrinkage above threshold confirm, for the first time, mid-infrared lasing in this structure on InP substrates. The lasing wavelength at 2.56 μm is the longest lasing wavelength at room temperature for the interband transition of InP-based material system.

High-Speed Optical Label Recognition Technique Using an Optical Digital-to-Analog Conversion and Its Application to Optical Label Switch

Operation performance of a 40 Gbps, 2-bit Optical Digital-to-Analog converter (ODAC) and its application to optical label switching systems have been investigated. The device is composed of a 1 × 2 multi-mode interference (MMI) splitter, one-bit-delay line, and a 2 × 1 MMI combiner. It has a high-mesa structure fabricated on InP-based materials. Dependence of output signal level on input signal wavelength and device temperature was measured. Due to the optical phase variation caused by the refractive index change with wavelength and temperature, output signal level varied, and it agreed well with simulation results. Four-level signals were generated and a quarter dependence of phase on temperature and wavelength compared with that for 10-Gbit/s was verified. Next, operation tolerance of the ODAC as an optical label processor, bit error rate (BER) of the digital-to-analog (DA)-converted signal was simulated. The tolerance against fluctuation of light source power, optical phase in the device, optical chirp, and extinction ratio of input signal was estimated. For all parameters, operation tolerance could be kept, but that for 40 Gbps is smaller than that for 10 Gbps. Then, autonomous label processing and optical label switching performance using a gate pulse generation scheme based on phase-shifted preamble was investigated. Optical DA conversion and three kinds of optical label were recognized at a bit rate of 40 Gbps, and optical packet transfer could be confirmed.

Fabrication of submicron-sized features in InP/InGaAsP/AlGaInAs quantum well heterostructures by optimized inductively coupled plasma etching with Cl2/Ar/N2 chemistry

Inductively coupled plasma dry etching for the fabrication of fine-pitch patterns in a wide range of InP-based materials has been developed. The effect of plasma chemistry (the N2 content in the total Cl2/Ar/N2 gas mixture) on the degree of undercut in the sidewall profile and surface morphology has been studied. Optimization of the etch process conditions produces strong passivation effects on the sidewalls, together with a highly anisotropic process, while still maintaining a good etch rate (560–730 nm/min). Single-step etching using hydrogen silsesquioxane as a resist/hard-mask resulted in high aspect ratio features being obtained (up to 30:1). Low plasma excitation power (inductively coupled plasma machine operating power of 400 W) and moderate ion energy (rf power of 120 W) were utilized to minimize etch-induced damage and provide low scattering losses. Low-loss (&amp;lt;0.3 dB/mm) optical ridge waveguides and high reflectivity and high-wavelength selectivity (Δλ=2 nm) results with 236 nm period sidewall gratings were demonstrated experimentally.

Modal Behavior of Photonic Crystal Tapers for Improved Coupling Toward Cleaved-Facet Single-Mode Fiber

We report simulation and experiment results of modal behaviors of photonic crystal (PhC) tapers on InP-based materials designed to improve coupling efficiency of the PhC waveguide mode into a cleaved-facet single-mode fiber. The modal distributions of transmitted power are simulated by two-dimensional finite difference time domain (2D-FDTD) calculation and the measured far-field patterns are in agreement with these calculations. The 34.4 mum-long PhC taper with Gaussian curve geometry is demonstrated to have an enhancement of coupling efficiency by a factor of four compared to the direct coupling from a W3 PhC defect waveguide.