Photonic Crystal Mirrors Research Articles

Photonic crystal mode terahertz lasers

We present the design and fabrication of photonic crystal (PhC) based resonators for terahertz quantum-cascade laser with a gain maximum at 2.7 THz. The PhC provides the confinement in lateral direction, for the vertical confinement a double-metal waveguide is used. We show theoretical and experimental analyses of devices based on a central gain region, which is surrounded by a PhC mirror. The devices are lasing in the bandgaps or at high-symmetry points of the PhC, depending on the period. These concepts allow us to tune the emission of the lasers in the range of a few hundred gigahertz.

High quality factor photonic crystal nanobeam cavities

We investigate the design, fabrication, and experimental characterization of high quality factor photonic crystal nanobeam cavities in silicon. Using a five-hole tapered one-dimensional photonic crystal mirror and precise control of the cavity length, we designed cavities with theoretical quality factors as high as 1.4×107. By detecting the cross-polarized resonantly scattered light from a normally incident laser beam, we measure a quality factor of nearly 7.5×105. The effect of cavity size on mode frequency and quality factor was simulated and then verified experimentally.

A Large-Area High-Reflectivity Broadband Monolithic Single-Crystal-Silicon Photonic Crystal Mirror MEMS Scanner With Low Dependence on Incident Angle and Polarization

In this paper, we introduce a single-axis resonant combdrive microelectromechanical systems (MEMS) scanner with a large-area highly reflective broadband monolithic single-crystal-silicon (SCS) photonic crystal (PC) mirror. PC mirrors can be made from a single monolithic piece of silicon through alternate steps of etching and oxidation. This process allows the fabrication of a stress-free PC reflector in SCS with better optical flatness than deposited films such as polysilicon slabs on low-index oxide. PC mirrors can be made in IR transparent dielectric material and can achieve high reflectivity over a broad wavelength range. PC reflectors have several advantages over other mirror technologies. They can tolerate much higher processing temperatures and higher incident optical powers as well as operate in more corrosive environments than metals. Compared to multilayer dielectric stacks, PC mirrors allow for simpler process integration, thus making them highly compatible with CMOS and MEMS processing. In this paper, we fabricate a PC mirror MEMS scanner in SCS without any deposited films. Our PC mirrors show broadband high reflectivity in the wavelength range from 1550 to 1600 nm, and very low angular and polarization dependence over this same range. The single-axis MEMS scanners are fabricated on silicon-on-insulator (SOI) wafers with the PC mirrors also fabricated in the SOI device layer. The scanners are actuated by electrostatic comb drives on resonance. Dynamic deflection measurements show that the scanners achieve 22deg total scan angle with an input square wave of 67 V and have a resonance frequency of 2.13 kHz.

Optical Characterization of High-Order 1-D Silicon Photonic Crystals

In this paper, we present numerical and experimental results on the spectral reflectivity of hybrid, high-order (up to 22nd) 1-D silicon photonic crystals (PCs) in the near-infrared region (wavelength range 1- 1.7 mum). Mechanically robust, vertical 1-D PCs with high aspect ratio and spatial period of 8 mum were fabricated by electrochemical micromachining of silicon, and tested in reflection with an improved optical setup, incorporating standard telecommunication single-mode optical fibers and a lensed fiber pigtail. A detailed theoretical, numerical analysis was performed to assess the effects of both non-idealities of the structures under test and constraints of the optical setup, on the spectral reflectivity. Experimental data were found in very good agreement with theoretical calculations, performed by using the characteristic matrix method, keeping into account an in-plane porosity variation for 1-D PCs, due to surface roughness of silicon walls, and the limited resolution bandwidth of the spectrum analyzer. Best optical performances, measured on the fabricated 1-D PC mirrors, consist of optical losses less than 0.8 dB in a bandgap around 1.5 mum and a -35 dB reflectivity minimum at a bandgap edge.

Double-heterostructure photonic crystal lasers with lower thresholds and higher slope efficiencies obtained by quantum well intermixing

In order to reduce the optical absorption loss, an array of double-heterostructure photonic crystal microcavity lasers was fabricated in which much of the photonic crystal mirror region was disordered by quantum well intermixing. In characterizing these devices, we obtained more than a factor of two increase in slope efficiencies and more than 20% reduction in threshold pump powers compared to devices that were not intermixed.

Single higher-order transverse mode operation of a radially polarized Nd:YAG laser using an annularly reflectivity-modulated photonic crystal coupler

We demonstrate single higher-order transverse mode operation of a radially polarized Nd:YAG laser by using a polarization-selective and reflectivity-modulated output coupler. A narrow annular region with low reflectivity fabricated in a photonic crystal mirror behaves so as to select a higher-order transverse mode of a cylindrically symmetric laser beam. A double-ring-shaped radially polarized TM(02) mode beam is stably generated.

Degenerate four-wave mixing based all-optical wavelength conversion in a semiconductor optical amplifier and highly-nonlinear photonic crystal fiber parametric loop mirror

The idler is separated from the co-propagating pump in a degenerate four-wave mixing (DFWM) with a symmetrical parametric loop mirror (PALM), which is composed of two identical SOAs and a 70m highly-nonlinear photonic crystal fiber (HN-PCF). The signal and pump are coupled into the symmetrical PALM from different ports, respectively. After the DFWM based wavelength conversion (WC) in the clockwise and anticlockwise, the idler exits from the signal port, while the pump outputs from its input port. Therefore, the pump is effectively suppressed in the idler channel without a high-speed tunable filter. Contrast to a traditional PALM, the DFWM based conversion efficiency is increased greatly, and the functions of the amplification and the WC are integrated in the smart SOA and HN-PCF PALM.

Direct production of high-power radially polarized output from a side-pumped Nd:YVO_4 bounce amplifier using a photonic crystal mirror

We produced a high power radially-polarized output directly from a diode-pumped Nd:YVO(4) bounce amplifier, using an autocloned photonic crystal mirror as an output coupler, with a simple cavity configuration. The radially-polarized output power of approximately 6 W was achieved, and a corresponding slope efficiency was estimated to be approximately 17 %. The output was characterized to be an ideal radially-polarized beam from its polarization distribution profiles. The output mode was not an eigenmode in the resonator. We discussed and clarified intra-cavity mode dynamics in terms of polarization distribution in the wavefront.

Direct production of high-power radially polarized output from a side-pumped Nd:YVO_4 bounce amplifier using a photonic crystal mirror

We produced a high power radially-polarized output directly from a diode-pumped Nd:YVO4 bounce amplifier, using an autocloned photonic crystal mirror as an output coupler, with a simple cavity configuration. The radially-polarized output power of ~6 W was achieved, and a corresponding slope efficiency was estimated to be ~17 %. The output was characterized to be an ideal radially-polarized beam from its polarization distribution profiles. The output mode was not an eigenmode in the resonator. We discussed and clarified intra-cavity mode dynamics in terms of polarization distribution in the wavefront.

Doppler Optomechanics of a Photonic Crystal

A laser beam directed at a mirror attached onto a flexible mount adds friction to its mechanical motion by the Doppler effect. For a normal mirror the efficiency of this radiative Doppler friction is very weak and practically masked by laser shot noise. We find that it can become very efficient using a photonic crystal mirror near its photonic band gaps. As an example, a Bragg mirror used at the long wavelength edge of its band stop can be efficiently optically cooled using the Doppler friction. The opposite effect opens new routes for optical pumping of mechanical systems: a laser pointing at a Bragg mirror and tuned at its short wavelength edge induces amplification of the vibrational excitation of the mirror leading eventually to its self-oscillation. These new effects rely on the strong dependency of a photonic crystal reflectivity on the wavelength.

Tapered Photonic Crystal Microcavities Embedded in Photonic Wire Waveguides With Large Resonance Quality-Factor and High Transmission

We present the design, fabrication, and characterization of a microcavity that exhibits simultaneously high transmission and large resonance quality-factor (Q-factor). This microcavity is formed by a single-row photonic crystal (PhC) embedded in a 500-nm-wide photonic wire waveguide - and is based on silicon-on-insulator. A normalized transmission of 85%, together with a Q-factor of 18 500, have been achieved experimentally through the use of carefully designed tapering on both sides of each of the hole-type PhC mirrors that form the microcavity. We have also demonstrated reasonably accurate control of the cavity resonance frequency. Simulation of the device using a three-dimensional finite-difference time-domain approach shows good agreement with the experimental results.

GaSb-based lasers with two-dimensional photonic crystal mirrors

We present the realization of two-dimensional (2D) photonic crystals (PhCs) on the GaSbmaterial system. An electron cyclotron resonance reactive ion etch process usingCl2/Ar allows the fabrication of PhCs covering air fill factors off = 20%–50%, latticeperiods of a = 400–500 nm and aspect ratios of 5:1. Quality and reflectivity of these structuresare evaluated by incorporating the PhCs as high reflective back mirrors inGaSb-based ridge waveguide lasers with cavity lengths between 200 and1100 µm with thefront facet as cleaved. The shortest devices show remarkable threshold currents below 12 mA and efficienciesof 0.23 W A−1, yielding a maximum output power of almost 19 mW, proving the applicability of thechosen approach to numerous further concepts based on 2D PhCs on the GaSb materialsystem.

Design, Fabrication, and Characterization of an Ultracompact Low-Loss Photonic Crystal Corner Mirror

An ultracompact, low-loss, and broad-band corner mirror, based on photonic crystals, is investigated in this paper. Based on the theoretical analysis of the loss mechanism, the boundary layers of the photonic crystal region are revised to improve the extra losses, and the transmission characteristics are evaluated by using the 3-D finite-difference time-domain method. The device with optimized structure was fabricated on silicon-on- insulator substrate by using electron-beam lithography and inductively coupled plasma etching. The measured extra losses are about 1.1plusmn0.4 dB per corner mirror for transverse-electronic polarization for the scanning wavelength range of 1510-1630 nm. Dimensions of the achieved PC corner mirror are less than 7times7 mum2, which are only about one tenth of conventional waveguide corner mirrors.

External fibre Fabry–Perot acoustic sensor based on a photonic-crystal mirror

We demonstrate an acoustic sensor based on a Fabry–Perot interferometer formed by a single-mode fibre and an external silicon photonic-crystal mirror. Measurements in air indicate that this sensor has a relatively uniform frequency response up to at least 50 kHz, and detects pressures as low as 18 μPa Hz−1/2. This limit is four orders of magnitude lower than in similar types of acoustic fibre sensors. The sensor response agrees with mechanical calculations to within a few dB. We predict that this sensor has the potential to detect pressures as low as 600 nPa Hz−1/2, corresponding to the ambient thermal noise level in air at room temperature.

Compact and polarization controlled 1.55μm vertical-cavity surface-emitting laser using single-layer photonic crystal mirror

Vertical-cavity surface-emitting lasers (VCSELs) consist of a gain medium in which feedback is generally accomplished by two distributed Bragg reflectors (DBRs), for which sufficient reflectivity has to be achieved in order to obtain laser emission. As a consequence, DBRs generally consist of very thick layer stacks. In this letter, the authors report the realization of a VCSEL, of which the top mirror consists of a single-layer one-dimensional photonic crystal mirror (PCM). This PCM enables significantly improved device compactness and total polarization control, while providing a directive and single lateral mode emission.

Compact 1.55 µm room-temperature optically pumped VCSEL using photonic crystal mirror

Reported is the first realisation of a novel vertical cavity surface emitting laser (VCSEL), in which one of the Bragg mirrors is entirely replaced by a single-layer photonic crystal mirror (PCM). The presence of the PCM considerably enhances the vertical compactness of the device. Room-temperature singlemode laser emission has been obtained at 1.55 µm by optical pumping (pulsed regime), with a threshold power around 15 mW.

Photonic Crystal Microcavities in SOI Photonic Wires for WDM Filter Applications

We report on the design, fabrication, and optical characterization of silicon-on-insulator-based one-dimensional (1-D) photonic crystal (PhC) microcavities. The scope of this paper lies on filters for communication systems around 1.55-mum wavelength. Detailed calculations of filter performance against the relevant device layout parameters are given. Resonant cavity modes with quality factors as high as Qap630 in the 1.55- mum wavelength band were measured for filters comprised of two PhC mirrors containing 2 times 5 holes, that were 200 nm in diameter. This is the highest Q-value reported of such a filter up to now

A all-optical switching based on highly nolinear photonic crystal fiber Sagnac loop mirror

We designed a novel and low switching-power all-optical fiber switch. The highly nonlinear photonic crystal fiber and the bi-directional pumped Er-doped fiber amplifier are inserted into the Sagnac loop mirror simultaneously. The switching is realized based on cross-phase modulation because the symmetry of the loop is broken. The theoretical analysis shows that the switching-power is inverse proportional to the product of the amplifier gain and the nonlinear coefficient of the photonic crystal fiber. In our experiment, 40 mW switching-power and 15.9 dB switching-extinction are obtained; furthermore, the transmission of signal light is a cosine function of the peak power of the control pulse. All the results of experiment well agree with the theory.

Ultimate vertical Fabry-Perot cavity based on single-layer photonic crystal mirrors

Vertical Fabry Perot cavities (VFPC) have been extensively studied, especially for the realization of vertical-cavity surface emitting lasers (VCSELs). They are traditionally composed of two Distributed Bragg Reflectors (DBR) which reflectivity has to be sufficient in order to obtain highly resonant cavity, which is particularly necessary for laser emission in VCSELs. As a consequence, DBRs consist generally in very thick layer stacks. In this paper, we demonstrate the smallest conceivable high Q vertical Fabry-Perot cavity, using ultra-thin and highly-efficient photonic crystal slab mirrors instead of conventional DBRs, which enable moreover a control of the polarization.

Fabry-Perot etalons using colloidal photonic crystal mirrors

Fabry-Perot etalons have been fabricated with 3D colloidal photonic crystal mirrors. The colloid films were optimized for high reflection and low loss to provide good finesse values in the 1200-1700 nm spectral range. A cavity quality factor of 2400 and a finesse of 8 together with sharp 0.5 nm wide resonance transmission peaks are reported that attest to the relatively good optical quality of the three-dimensionally structured films and the promise of self-assembly colloidal crystal chemistry in providing novel microporous optical interferometers for potential applications such as environmental and biological sensing.