Micromechanical tunable vertical-cavity surface-emitting lasers.

摘要

Tunable lasers, filters, and detectors are useful in many applications including communications, spectroscopy, and beam steering. Typical tunable devices are constructed with bulk optics, making them expensive. To address this problem, integrated devices which tune with either carrier injection or temperature have received considerable attention in recent years. Although wide tuning ({dollar}Deltalambdagg{dollar} 1%) has been achieved, there have been several drawbacks to these devices. All methods to tune lasers have had to mode hop (i.e. they must discretely jump between wavelengths) to tune more than a few nanometers. Widley tunable filters and detectors with high extinction ratios have also proved difficult to build.; This thesis discuss a new tuning mechanism: micromechanical tuning of vertical cavities. Vertical cavities have several nice features, including circular modes, wide mode spacing, no cleaved facets, compact size, wafer scale testing, and integrability into 2-D arrays. When coupled with micromechanical movement, wide ({dollar}Deltalambda/lambdagg{dollar} 1%) continuous tuning can be achieved with just a single electrical contact. Micromechanical movement is voltage-controlled and requires only {dollar}mu{dollar}W of tuning power compared to mW for other mechanisms.; Tunable filters, tunable detectors, and the first micromechanical tunable vertical cavity surface emitting laser (VCSEL) were fabricated. The optical and mechanical performance of these devices closely agrees with calculations. In all three cases record tuning ranges were achieved. New fabrication techniques, including the use of wet oxidation of AlAs, resulted in a dramatic improvement in device performance. With these improvements, VCSELs were obtained with 19.1 nm of tuning. To the best of our knowledge, this is the widest, continuous tuning range ever achieved with a monolithic semiconductor laser. We also achieved threshold currents of 460 {dollar}mu{dollar}A and peak powers of 0.9 mW. This represents the best device performance of micromechanical tunable VCSELs and the first demonstration of performance comparable to the best VCSELs.