CW blue-green light emission from GaN and SiC by sum-frequency generation and second harmonic generation

Abstract

GaN and SiC are wide band gap semiconductors (WBGS) well known for their chemical and thermal stability and are widely used in optoelectronics, 1,2 and high-power, high temperature 3,4 devices, respectively. The initial interest in GaN was centered on the fabrication of blue light emitting diodes (LEDs) and laser diodes. However, the band gap of GaN can also be tailored by alloying with In and Al to produce light emission from UV to infrared. Recently, the success of the incorporation of rare earth elements into GaN has ushered in a new technique of making light-emitting diodes. 5 On the other hand, the research and development in SiC technology has also produced significant progress over the past five years. A major factor in this rapid growth has been the development of SiC bulk crystals and the availability of crystalline substrates. An interesting, but less explored, area is the nonlinear optical (NLO) properties of these WBGS materials. Both GaN and SiC have large NLO coefficients. 6-8 By combining their excellent electronic/optical properties with NLO properties, a truly integrated optical circuit can be envisioned where light sources, detectors, modulators, switches and processing circuits can be fabricated monolithically. It has been shown that the second-order nonlinearities of GaN 6 and SiC 7,8 are an order of magnitude larger than Continuous wave (CW) back-scattered sum-frequency generation (SFG) and second harmonic generation (SHG) have been obtained from GaN and SiC. GaN samples were obtained from GaN films grown by molecular-beam epitaxy (MBE), metalorganic chemical-vapor deposition and hydride vapor-phase epitaxy. The SiC samples were obtained from 3C SiC/Si grown by chemical vapor deposition (CVD), 4H and 6H single crystal SiC substrates. The samples were optically excited with two CW lasers at the red (840 nm) and the infrared (1.0 µm). SHG at 420 nm and 500 nm and SFG at 455 nm were observed. SFG and SHG were verified by measuring their relative intensities against the pumping laser power. The SHG signals from GaN and SiC samples are compared with that from KH 2 PO 4 (KDP).

Plasmon-enhanced nonlinear optical properties of SiC nanoparticles

“…The photon energy of the emissions governed by this effect can be easily tuned throughout the visible spectral range by varying the size of the SiC NPs and the excitation energies [3,4]. At the same time, SiC is known to have extremely interesting nonlinear optical (NLO) properties which have been analyzed both theoretically and experimentally on a variety of SiC samples and polytypes [5][6][7][8][9][10]. In particular, as it is characterized by a relatively high damage threshold, SiC [11] can considerably improve device efficiency by increasing the operational power density for NLO applications.…”