Reducing Optical Losses in GaN Waveguides – Toward an Electro‐Optic Phase Modulator

Abstract

In recent years, gallium nitride (GaN) has been investigated as a potential material for various integrated photonic devices. A key component of integrated photonic devices is a voltage‐controlled phase modulator in an optical waveguide (WG) design. To date, the main obstacles in the realization of such a device are significant optical losses that are related to various mechanisms. In this research, the main factors for optical losses in a GaN phase modulator are experimentally studied. The suggested design is based on a reverse‐biased p–n junction ridge WG scheme. The losses are determined mainly using the Fabry–Perot method at a wavelength of 1064 nm, which is important for high‐optical‐power applications. The contribution of the ridge waveguide wall roughness losses, the p‐doped layer absorption, and the metallic p‐contacts is evaluated. Based on these results, an optimized structure of an electro‐optical GaN phase modulator is proposed. The modulator voltage response is calculated while taking optical polarization effects into account.

High‐Electron‐Mobility Transistor‐Inspired Freestanding AlGaN/GaN/AlN Optical Waveguide for High‐Pressure Sensing Applications

“…In addition, the photonic absorption is negligible above 730 nm. [ 17 ] Recently, Das et al proposed HEMT‐inspired electro‐optic modulator topologies at the heterostructure interfaces where the phase shift is very limited and the observed phase shift is comparatively less than 1 × 10 −5 rad. [ 14 ] For increasing the phase shift, the same group utilized high contrast gratings in AlGaN/GaN heterostructure.…”

Organic Electro‐Optic Mach–Zehnder Modulators: From Physics‐Based to System‐Level Modeling

“…[ 5 ] (Recently, also III‐N semiconductors have been proposed as EOM candidates. [ 6 ] ) While III–V semiconductors and perovskites exhibit the linear (Pockels) EO effect, silicon features only the much weaker quadratic (Kerr) effect. Si‐based integrated photonics (SiPh) has, however, seen an impressive development during the past few years, as it offers the possibility to realize, with processes compatible with complementary metal‐oxide semiconductor (CMOS‐compatible) integrated circuits, wideband photonic and optoelectronic elements directly integrable with digital or analog electronic subsystems.…”

Growth and fabrication of GaN/Er:GaN/GaN core-cladding planar waveguides

“…Most of the previously studied GaN waveguide structures were based on undoped or unintentionally doped GaN thin epilayers of a few microns in thickness for passive integrated photonic device applications. [20][21][22] Waveguide structures incorporating $0.5 lm thick Er:GaN were fabricated on sapphire substrates for studying the basic optical properties, including the carrier lifetime, 23 excitation and absorption cross sections, 24,25 and optical loss. 26 Waveguide based Er doped GaN and InGaN thin epilayers were fabricated to demonstrate the optical amplification effect under band-edge excitation targeting for applications in chip-scale optical communications.…”