Dan Bai

Angular-dependent polarization-insensitive filter fashioned with zero-contrast grating

We report here an angular-dependent polarization-insensitive filter fashioned with a free-standing zero-contrast grating (ZCG), which is implemented on an HfO(2)/Silicon platform. The spectral characteristics are investigated by rigorous coupled-wave analysis method and measured on angular-resolved micro-reflectance system. The proposed ZCG structure experimentally shows that the polarization-insensitive resonances occur at 595nm for the incidence angle θ of 12.8° and 500nm for the incidence angle θ of 14.2°. When the incident light is normal to the grating surface, the ZCG device generates yellow and red colors for p- and s-polarization, respectively. The experimental results are in good agreement with the simulations, which indicate that the free-standing ZCG device is promising for polarization-insensitive filter and polarization-controlled tunable color filter.

Monolithic integration of a suspended light-emitting diode with a Y-branch structure

We describe a double-sided process for the monolithic integration of a light-emitting diode (LED) and a Y-branch structure on a GaN-on-silicon platform. The suspended LED and highly confined waveguides are fabricated by silicon removal with back-side thinning of the suspended membrane. When the LED is turned on, part of the light emission is confined by a suspended rectangular waveguide, and the light propagates laterally. The guided light is then coupled into two branching rectangular waveguides and diffracted into the air at the output facets. The light output can be tuned by the LED, opening the potential for more sophisticated integrated photonic circuits.

Wideband reflectors fashioned with freestanding HFO 2 resonant gratings

This paper proposes the design and fabrication of guided-mode resonant broadband reflectors operating in the visible band under TE polarization. The structure is composed of a freestanding subwavelength periodic HfO2 grating with an air cavity between the grating and the silicon substrate. The proposed wideband reflectors fashioned with freestanding HfO2 resonant gratings are implemented on an HfO2/AlN/Silicon platform by combining ion beam etching (IBE) of HfO2 film and wet etching of AlN. The optical responses of the designed freestanding HfO2 gratings are analyzed by the rigorous coupled-wave analysis(RCWA) method. More than 98% reflectance over an 50~52nm spectral range spanning 396~470nm was shown in the simulation of two reflectors with different parameters.

Visible light propagation inside free-standing InGaN/GaN quantum-well rib waveguides

This paper describes a double-side process to fabricate free-standing InGaN/GaN multiple quantum wells (MQWs) rib waveguides on a GaN-on-silicon platform. The large index contrast between GaN and air imposes a strong optical confinement of the rib waveguide structures. When the light is generated from InGaN/GaN MQWs, part of the excited light is guided and propagates within the rib waveguide. Experimental and simulation results show that multiple light losses will reduce the light propagation distance, and back wafer etching of free-standing membrane is an effective way to decrease the light loss and to increase the light propagation distance. The performance of the light propagating inside the orthogonal waveguides illustrates that the rib waveguide structures can be utilized to control the light propagation direction inside the waveguide, which is promising for the development of diverse beam splitters for further integrated photonic circuit in the visible wavelength range.