Liquid crystal-based tunable photodetector operating in the telecom C-band

Area of Science:

• Optoelectronics
• Materials Science
• Photonics

Background:

• Indium Gallium Arsenide (InGaAs) photodiodes (PDs) are crucial for optical detection.
• Liquid crystals (LCs) offer tunable optical properties.
• Integrating LC microcells with PDs can create novel tunable optical devices.

Purpose of the Study:

• To demonstrate monolithic integration of LC microcells onto InGaAs PDs.
• To characterize the wavelength tunability and performance of these integrated devices as tunable filters.
• To assess the potential application of these tunable PDs as micro-spectrometers.

Main Methods:

• Fabrication of InGaAs PDs with monolithically integrated LC microcells.
• Optical characterization using a tunable laser source (S and C bands).
• Photocurrent measurements to determine device sensitivity and spectral response.
• Analysis of spectral linewidth (Full Width at Half Maximum - FWHM).

Main Results:

• Demonstrated LC microcells acting as tunable Fabry-Perot filters.
• Achieved wavelength tunability exceeding 100 nm around 1550 nm with <10V applied voltage.
• Observed an average sensitivity of 0.4 A/W over a 70 nm tuning range (<7V).
• Maintained a constant spectral linewidth (FWHM) of 1.5 nm.

Conclusions:

• Successful monolithic integration of LC microcells on InGaAs PDs.
• These tunable PDs function effectively as micro-spectrometers.
• The devices show significant potential for compact and tunable optical sensing applications.