Second harmonic generation in GaN transverse quasi-phase-matched waveguide pumped with femtosecond laser

Abstract

A wavelength conversion device with an input grating coupler that enables easy alignment was fabricated using a vertically polarity inverted GaN layer. The device was excited with a femtosecond laser, and a second harmonic wave with a peak wavelength of 438.4 nm was obtained. A normalized wavelength conversion efficiency of 4.7  10−4%W−1 and a spectral bandwidth of the second harmonic wave of 2.9 nm were comparable to the theoretical estimations taking into account serious walk-off and waveguide losses. High efficiency of 33-34%W−1 can be expected under continuous-wave excitation.

229 nm far-ultraviolet second harmonic generation in a vertical polarity inverted AlN bilayer channel waveguide

“…The wide spectral bandwidth of the SH light would be caused by group velocity walk-off between the pump and SH ultrashort pulses. 22) The peak intensity of the SH light was proportional to the square of the average pump power as shown in Fig. 4(b).…”

“…In our previous work, blue SHG at 438 nm was demonstrated from the transverse QPM GaN channel waveguide. 22) Vertical polarity inversion of AlN layers by epitaxial growth has been reported. [23][24][25] In this study, a transverse QPM SHG channel waveguide with a vertically polarity inverted AlN bilayer was designed.…”

“…The normalized wavelength conversion efficiency η SH has not been estimated experimentally here, but is roughly estimated to be 10 −4 % W −1 assuming a d 33 of 6.3 pm V − 1 15) and no waveguide loss using the theoretical calculation reported in Ref. 22. Our quantitative efficiency determination for the case of blue SHGs from GaN transverse QPM channel waveguides with ultrashort pulse excitation indicates that η SH should be also lower for AlN-based SHGs due to the short effective interaction length of about 20 μm, caused by the severe walk-off between the fundamental and SH wave peak positions due to group velocity dispersion.…”

Control of Polarity of AlN Grown on Sapphire Substrate and Growth with Both Al‐ and N‐Polarities

“…[ 11 ] Another method involved fabrication via epitaxial growth of an AlO x N y layer on the lower N‐polar GaN layer, and SHG operation was achieved. [ 12 ] However, the nonuniform thickness of the channel waveguide may be problematic. Lateral polar structures (LPSs) are fabricated via crystal growth.…”

Second harmonic generation from a-plane GaN vertical monolithic microcavity pumped with femtosecond laser

“…[9][10][11][12][13] SPDC devices are popular choices for light sources for quantum optical circuits 14,15) Nitride semiconductors such as GaN and AlN are suitable for wavelength conversion devices because they have large optical nonlinearity comparable to ferroelectric materials, wide transparent wavelength range, and high optical damage tolerance which exceeds them. [16][17][18][19][20][21] AlN can be applied to the DUV SHG devices pumped by blue/ green lights. GaN and AlN have excellent transparency from infrared to ultraviolet region, and they can be applied to the near-infrared quantum entangled photon pair generation device pumped by blue lights.…”