Passive cavity surface emitting laser

Abstract

Demonstrated is a vertical cavity surface emitting laser (VCSEL) formed by a passive half-wavelength cavity and a quarter-wavelength active gain region, wherein the said gain region resides in one of the VCSEL's distributed Bragg reflectors. The device concept invites extensive opportunities for innovation in the combinations of materials and gain region placements that may be used to construct surface emitting devices.Introduction: GaAs-based vertical cavity surface emitting lasers (VCSELs) [1] are broadly used in sensing and optical communications.The key advantages of VCSELs include a low threshold current density, high power conversion efficiency, narrow emission spectrum, high temperature stability, planar processing, high yield, and high reliability. More recently, photonic crystal VCSELs [2, 3] opened a way to engineer singlemode polarisation stable VCSELs with large apertures, realise field-coupled arrays, and produce lasers with different emission wavelengths on the same wafer. Yet still the industrial progress of VCSELs is limited by the GaAs-AlGaAs materials system. This system provides a relatively high refractive index step for wavelengths longer than about 750 nm between its binary and quasi-binary members, and thus relatively thin and highly-reflective distributed Bragg reflectors (DBRs) with significant heat conductivity. Despite notable success in basic research [4], industrial applications of InP-, GaSb-, GaN-, and short wavelength (red) GaAs-based VCSELs [5] remain quite limited or in full stasis. For these VCSEL products the main obstacle for broader market penetration is the small step in the refractive indices of the DBRs. As is well known, a small index contrast in monolithic semiconductor DBRs leads to a narrow DBR stopband. The narrow-band DBRs must be grown with extreme precision and a large number of periods to provide the necessary power reflectance for lasing. Moreover, in low index contrast VCSELs the resonant optical field intensity significantly extends outside of the microcavity region. This reduces modal gain and heat conductivity and leads to inefficient devices.In this Letter we report the performance of oxide-confined 850 nm GaAs-based VCSELs with an InAs submonolayer quantum dot [6] active region incorporated into a high-index l/4-thick section of the top DBR, wherein the gain region is displaced five DBR periods from a passive cavity region. The optical field intensity in the VCSEL's cavity is generated by the gain section with a gain maximum spectrally within the forbidden gap of the DBR. The passive resonant cavity can be made of a large variety of materials including dielectric layers that may or may not be lattice matched and have a large refractive index step. The passive resonant cavity may contain for example: metal insertions, materials with a compensated dependence of the refractive index on temperature, an electro-optic or -absorption modulator, a photonic crystal structure, or a nanometre-patterned medium. Since the optical field intensity in the cavity and the wi...

Дизайн и новая функциональность антиволноводных вертикально-излучающих лазеров на длину волны 850 nm

“…Для уменьшения сдвига и создания возможности большего уплотне-ния каналов в том же спектральном диапазоне (850−950 nm) была предложена концепция вертикально-излучающего лазера с пассивной полостью (passive-cavity surface-emitting laser) [7,11].…”

“…Несмотря на это, структура вертикального лазера с пассивной полостью, целиком основанная на полупроводниковых материалах, показала лазерную ге-нерацию [11]. Для структуры с диэлектрической полостью и апертурой диаметром ∼ 3 µm в спектрах ЭЛ наряду с длинноволновым пиком, соответствующим фундаментальной моде (расщеплен по поляризации), наблюдаются более коротковолновые пики от мод высокого порядка (рис.…”

Application of nanophotonics to the next generation of surface-emitting lasers

“…The first realization of a passive cavity laser is an allsemiconductor VCSEL-type device in which the active medium is placed in a top DBR ( Figure 4A) [23].…”

“…In spite of the three thick oxide aperture layers, SM or quasi-SM operation is observed up to aperture diameters of ~ 6 μm. Figure 5 illustrates a modeled passive cavity VCSEL having a dielectric cavity and a dielectric top DBR, having a zero thermal shift of the resonant wavelength [23].…”

Magnetically controlled vertically emitting laser with anisotropic pumping

“…A conventional surface emitting laser with a verti cal resonator represents a 1D photonic crystal (Bragg mirror) with a resonant cavity [5][6][7][8][9][10][11][12]. The generated radiation in such a device is directed perpendicularly to the layer surface.…”