Piezoelectricallyactuated MEMStunable Vertical Cavity Surface Emitting Laser VCSEL

Piezoelectrically-actuated MEMS-tunable Vertical Cavity Surface Emitting Laser (VCSEL) Benjamin Cheng, Mike Huang Advisors: Albert P. Pisano, Connie Chang-Hasnain Goals: A novel piezoelectrically-actuated microelectromechanical system (MEMS) tunable vertical-cavity surface emitting laser (VCSEL) is to be designed, fabricated and evaluated to provide improved wavelength control with lower power supply voltages and reduced external losses © 2006 University of California Prepublication Data Spring 2006

Motivation Top DBR Bottom DBR • • VCSEL + MEMS = Ideal tunable laser – wide and continuous wavelength tuning Limitation of electrostatic actuation • Piezo-electric actuation – tuning range (1/3 of airgap) – Linear and fast response – catastrophic damage in pull-in – no deflection limitation – no catastrophic damage – consume very low power © 2006 University of California Prepublication Data Spring 2006

Piezo-MEMS VCSEL Design tuning contact laser output laser contact Cantilever-VCSEL n-doped Suspended top DBR intrinsic p-doped airgap p-Ga. As top mirror p-DBR λ-cavity n-DBR Ga. As substrate © 2006 University of California Prepublication Data Spring 2006 bottom mirror

Fabrication © 2006 University of California Prepublication Data Spring 2006

RT CW tuning spectra at 1. 3 Ith Cantilever: 120μm x 15μm Aperture: ~5μm tuning spectra tuning curve and IV characteristic ~1 nm tuning piezo tuning Blue-shift • • Continuous wavelength tuning ~1 nm from -10 V to 5 V Requires very low actuation power ~1μW © 2006 University of California Prepublication Data Spring 2006 saturation

Conclusion • First demonstration of monolithic integrated piezo-electric actuated MEMS tunable VCSEL – utilizing inherent piezoelectric properties of Al. Ga. As compound – precise and continuous wavelength tuning (~1 nm) – low power consumption (~1μW) for actuation – linear tuning characteristic simplifies electronic control • Work in progress to increase wavelength tuning – optimization of the electrical and mechanical design for ~10 nm tuning – Characterization of Brownian noise effect on tuning spectra © 2006 University of for California Prepublication Data Spring 2006 – Feedback control higher thermal stability