MEMS-based VCSEL reaches record 150 nm tuning range

Last year, Laser Focus World reported on a microelectromechanical systems (MEMS)-based 1310 nm widely tunable vertical-cavity surface-emitting laser (VCSEL) from Praevium Research (Santa Barbara, CA), Thorlabs (Newton, NJ), Advanced Optical Microsystems (AOMicro; Mountain View, CA), and the Massachusetts Institute of Technology (MIT; Cambridge, MA) that enabled 760 kHz optical coherence tomography (OCT) scanning in conjunction with a 110 nm tuning range. A year later, the same research group has reached new heights with a 150 nm tuning range at 1310 nm—the widest tuning range reported for any VCSEL at any wavelength.

MEMS-based VCSEL achieves 150 nm tuning range via movable suspended mirror

The record tuning range was made possible through an improved cavity and electrostatic actuator design. These MEMS-based VCSELS essentially consist of a lasing cavity in which the top mirror is suspended on a MEMS actuator. Tunability was expanded by using a thinner cavity in an optically pumped configuration. Optical pumping eliminates resistive heating and the need to dope the mirrors and cavity, significantly reducing free-carrier absorption and subsequently reducing threshold gain for lasing over a wider portion of the gain spectrum. The new devices use a shorter total cavity length that extends the free-spectral range. Wideband mirrors and wider-gain indium-phosphide (InP)-based quantum wells also promote an expanded tuning range. Contact Vijaysekhar Jayaraman at vijay@praevium.com.

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