Vertically emitting annular Bragg lasers using polymer epitaxial transfer

Abstract

Fabrication of a planar semiconductor microcavity, composed of cylindrical Bragg reflectors surrounding a radial defect, is demonstrated. A versatile polymer bonding process is used to transfer active InGaAsP resonators to a low-index transfer substrate. Vertical emission of in-plane modes lasing at telecom wavelengths is observed under pulsed optical excitation with a submilliwatt threshold. Recently, a new ring cavity geometry, based on optimally designed cylindrical Bragg reflectors surrounding a radial defect, was proposed. 14,15 Resonators of this class, known as annular Bragg resonators (ABRs), are designed to support azimuthally propagating modes, with energy concentrated within the defect region by radial Bragg reflection. Optical modes with an electric field having the form E͑r , , z͒ = E͑r , z͒e im have been analyzed using several techniques, including conformal transformation, a transfer matrix approach, coupled mode theory, and finite-difference time-domain simulations. ABR devices are of great interest for their superior sensitivity in biological and chemical sensing applications when compared to conventional total internal reflection (TIR) based resonators. 16 This letter describes the fabrication and experimental demonstration of laser action in a semiconductor annular Bragg resonator.Annular Bragg resonators with high contrast Bragg reflectors were realized in active semiconductor material. The semiconductor medium consisted of a 250-nm-thick InGaAsP layer (n Ϸ 3.35 at = 1.55 m) on top of an InP substrate. The InGaAsP layer included six 75-Å-wide compressively strained InGaAsP quantum wells positioned at the center, with peak photoluminescence occurring at 1559 nm. Epitaxial layers were grown by MOCVD.The ABR fabrication process, illustrated in Fig. 1, proceeded as follows. First, a SiO 2 etch mask layer was deposited by PECVD. A layer of PMMA electron beam resist was then applied by spin-coating. The desired ABR geometry was then defined using a Leica Microsystems EBPG 5000+ direct electron beam writer operating at 100 kV. After development, the PMMA patterns were transferred into the SiO 2 etch mask layer by inductively coupled plasma reactive ion etching (ICP-RIE) using C 4 F 8 plasma. The remaining PMMA was removed with a gentle isotropic O 2 plasma step. The SiO 2 then served as a hard mask for pattern transfer into the active InGaAsP layer, using an ICP-RIE etch employing HI / Ar chemistry. 17 The patterns were etched to a depth of ϳ325 nm. The remaining SiO 2 hard mask was then stripped in a buffered hydrofluoric acid solution. A scanning electron microscope (SEM) image of an ABR device at this stage is shown in Fig. 2(a). To achieve strong vertical confinement, the InGaAsP membrane must be clad by low-index material both above and below. An epitaxial layer transfer technique, 18 using an UV-curable optical adhesive (Norland Products NOA 73, n Ϸ 1.54 at = 1.55 m), was adopted to flip-bond the patterned semiconductor sample to a transparent sapphire substrate. Subsequently, the

A circular dielectric grating for vertical extraction of single quantum dot emission

“…It is based on (linear) high-contrast second-order Bragg gratings recently introduced 4 for light extraction from planar waveguides. While similar circular geometries have been employed for enhanced light extraction from light emitting diodes, 5 and for demonstrating annular Bragg lasers, 6 here we show an application in QD single photon extraction.The design process consisted of a series of finite difference time domain simulations that maximized vertical light extraction near the expected QD s-shell emission (k QD % 940 nm), by varying K, t, and w. The structures were excited with a horizontally oriented electric dipole at the bullseye center (x ¼ 0, y ¼ 0), representing an optimally placed QD. Total radiated power, steady-state upwards emission, and electromagnetic Electronic mail: mdavanco@nist.gov.…”

“…It is based on (linear) high-contrast second-order Bragg gratings recently introduced 4 for light extraction from planar waveguides. While similar circular geometries have been employed for enhanced light extraction from light emitting diodes, 5 and for demonstrating annular Bragg lasers, 6 here we show an application in QD single photon extraction.…”

Electrically-pumped, broad-area, single-mode photonic crystal lasers

“…After resist development, the PMMA patterns are transferred into the SiO 2 layer by reactive ion etching (RIE) using a CHF 3 plasma. The SiO 2 layer then serves as a hard mask to etch the semiconductor using an inductively coupled plasma RIE (ICP-RIE) with HI/Ar chemistry [17].…”

Surface-emitting circular DFB, disk- and ring- Bragg resonator lasers with chirped gratings: a unified theory and comparative study

“…Among the various grating coupled schemes, circular grating lasers with large emission apertures possess the additional advantage of producing circularly-symmetric, narrow-divergence laser beams, making them convenient for coupling to fibers [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. In such lasers, the grating serves two purposes: confining the in-plane fields to form a radial resonator and secondly acting as a broadside output coupler.…”