TiO2 membrane high-contrast grating reflectors for vertical-cavity light-emitters in the visible wavelength regime

Hashemi, Ehsan; Bengtsson, Jörgen; Gustavsson, Johan S.; Carlsson, Stefan; Rossbach, Georg; Haglund, Åsa

doi:10.1116/1.4929416

Cited by 28 publications

(7 citation statements)

References 25 publications

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“…This reflects the advantage of flexible design for the proposed surface PhCs. TiO 2 has negligible absorption at a ~450 nm wavelength with a 2.55 refractive index [30][31][32]. This high refractive index will pull field distribution move to PhCs and thus obtain a high PhC confinement factor.…”

Section: Resultsmentioning

confidence: 99%

“…This high refractive index will pull field distribution move to PhCs and thus obtain a high PhC confinement factor. Besides, TiO 2 is a widely available material with compatible growth properties and can be easily fabricated as micro-nano structures, such as gratings and photonic crystals [31][32][33][34][35]. Different lattice constants and hole radius designs have the function of realizing different wavelength mode lasing, as illustrated in Figure 3.…”

Section: Resultsmentioning

confidence: 99%

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Investigation on GaN-Based Membrane Photonic Crystal Surface Emitting Lasers

et al. 2022

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A GaN-based blue photonic crystal surface emitting laser (PCSEL) featured with membrane configuration was proposed and theoretically investigated. The membrane dimension, photonic crystal (PhC) material, lattice constant and thickness were studied by RCWA (Rigorous Coupled Wave Analysis), FDTD (Finite Difference Time Domain) simulations with the confinement factor and gain threshold as indicators. The membrane PCSEL’s confinement factor of active media is of 13~14% which is attributed to multi-pairs of quantum wells and efficient confinement of the mode in the membrane cavity with air claddings. The excellent confinement factor and larger Q factor of resonance mutually contribute to the lower gain threshold of the design (below 400 cm−1 for GaN-PhC with 100 nm thick top and bottom GaN layer, 40 nm hole radius and 40 nm depth). The PhC confinement factor exceeds 13% and 6% for TiO2-PhC with 80 nm and 60 nm PhC thickness and 20 nm and 40 nm distance between PhC and active media, respectively. It is around two times larger than that of GaN-PhC, which is attributed to the higher refractive index of TiO2 that pulls field distribution to the PhC layer.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Investigation on GaN-Based Membrane Photonic Crystal Surface Emitting Lasers

et al. 2022

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“…In order to obtain high field coupling strength, the GaN-based active membrane with multi-quantum wells (MQWs) is combined with a top TiO2-based PhC layer, as shown as the schematic diagram in Fig. 1 TiO2 is a stable and widely used material, which has been successfully integrated in CMOS devices and micro-nano fabricated structures [20]- [23]. The RI of TiO2 is about 2.55 around 450 nm wavelength with a negligible absorption [20]- [22].…”

Section: Laser Design and Athermal Propertiesmentioning

confidence: 99%

“…1 TiO2 is a stable and widely used material, which has been successfully integrated in CMOS devices and micro-nano fabricated structures [20]- [23]. The RI of TiO2 is about 2.55 around 450 nm wavelength with a negligible absorption [20]- [22]. Such high RI is beneficial to the PCSEL's design which can regulate the mode distribution and further obtain a high confinement factor in the PhC layer.…”

Section: Laser Design and Athermal Propertiesmentioning

confidence: 99%

Design of GaN-Based PCSEL With Temperature-Insensitive Lasing Wavelength

Liu

Wang

et al. 2021

IEEE Photonics J.

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Considering the compensation of thermo-optic coefficients (TOC) between GaN-based cavity and TiO2 photonic crystal (PhC) layer, we have theoretically designed a photonic crystal surface emitting laser (PCSEL) with temperature-insensitive wavelength. The structure includes a freestanding GaN membrane with embedded multiple InGaN/GaN quantum well (QW) layer and the top TiO2 PhC layer. The high refractive index (RI) of PhC and the freestanding membrane cavity structure cooperate to enable a stronger field-coupling in PhC, thus fulfill the athermal coupling condition. Interestingly, the wavelength temperature dependence is only 0.0015 nm/°C for such PCSEL with a 82% PhC confinement factor, and its athermal property is proportional to the field confinement factor in TiO2 PhC layer. To illustrate, a general formula has been developed after the investigations of thermo-optic effect and thermal expansion effect.

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“…An HCG comprises one layer of subwavelength gratings that is constructed by two different dielectric materials with a relatively large refractive index difference . The HCG has several advantageous characteristics such as a comparatively wide stopband, − thin mirror thickness, and high polarization selectivity over the reflection. In order to fulfill the largest refractive index contrast, the HCG is in most cases of a membrane type, that is, suspended and thus surrounded by low refractive index material on both sides.…”

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confidence: 99%

Electrically Injected GaN-Based Vertical-Cavity Surface-Emitting Lasers with TiO₂ High-Index-Contrast Grating Reflectors

et al. 2020

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We demonstrate the first electrically injected GaN-based vertical-cavity surface-emitting lasers (VCSELs) with a TiO2 high-index-contrast grating (HCG) as the top mirror. Replacing the top distributed Bragg reflector (DBR) with an HCG offers substantial thickness reduction, polarization-pinning, and setting of the resonance wavelength by the grating parameters. Conventional HCGs are usually suspended in the low refractive index material, such as air, in order to create the largest refractive index contrast. However, the mechanical stability of such structures can be questioned and creating free-hanging GaN-membrane on top of GaN is problematic. We have therefore fabricated TiO2–HCGs resting directly on GaN without an air-gap. No DBR layers are used below the HCG to boost the reflectivity. A VCSEL with an aperture diameter of 10 μm shows a threshold current of 25 mA under pulsed operation at room temperature. The lasing modes locate around 400 nm and are transversely electrically -polarized with a line width of 0.5 nm. The full-width half-maximum beam divergence is 10°. This demonstration of a TiO2–HCG VCSEL offers a new route to achieve polarization pinning and could also allow additional benefits such as postgrowth setting of the resonance wavelength.

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TiO2 membrane high-contrast grating reflectors for vertical-cavity light-emitters in the visible wavelength regime

Cited by 28 publications

References 25 publications

Investigation on GaN-Based Membrane Photonic Crystal Surface Emitting Lasers

Investigation on GaN-Based Membrane Photonic Crystal Surface Emitting Lasers

Design of GaN-Based PCSEL With Temperature-Insensitive Lasing Wavelength

Electrically Injected GaN-Based Vertical-Cavity Surface-Emitting Lasers with TiO₂ High-Index-Contrast Grating Reflectors

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TiO2 membrane high-contrast grating reflectors for vertical-cavity light-emitters in the visible wavelength regime

Cited by 28 publications

References 25 publications

Investigation on GaN-Based Membrane Photonic Crystal Surface Emitting Lasers

Investigation on GaN-Based Membrane Photonic Crystal Surface Emitting Lasers

Design of GaN-Based PCSEL With Temperature-Insensitive Lasing Wavelength

Electrically Injected GaN-Based Vertical-Cavity Surface-Emitting Lasers with TiO2 High-Index-Contrast Grating Reflectors

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Product

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Electrically Injected GaN-Based Vertical-Cavity Surface-Emitting Lasers with TiO₂ High-Index-Contrast Grating Reflectors