F. Sugihwo

Low threshold continuously tunable vertical-cavity surface-emitting lasers with 19.1 nm wavelength range

Continuous wavelength tuning of 19.1 nm is reported for vertical-cavity surface-emitting lasers. Stress-matched dielectric mirror stacks are added to the micromachined deformable-membrane top mirror to enhance reflectance, resulting in devices with 6.5% quantum efficiency and threshold current as low as 0.34 mA. The laser operates in single mode near 968 nm with 24 dB mode suppression ratio and tuning voltages are below 18 V.

Simultaneous optimization of membrane reflectance and tuning voltage for tunable vertical cavity lasers

Micromachined wavelength tunable vertical cavity lasers are attractive for applications ranging from wavelength division multiplexing to spectroscopy. An improved tunable structure that incorporates a partial anti-reflection coating to increase coupling between the air gap and the semiconductor cavity, and a more flexible micromachine process that enables independent optimization of the central reflector region and deformable membrane structure are described. This combination of structural and process modifications enables decoupling the tradeoffs between wavelength tuning rate and threshold current, as well as the tradeoffs between top mirror reflectance and tuning voltage. With these improved approaches, a 2.5 pair dielectric distributed Bragg reflector hybrid membrane top mirror produced singlemode devices with a 23 nm wavelength tuning range and multi-transverse-mode devices with a 30 nm wavelength tuning range. Threshold current, differential quantum efficiency, and lasing mode are characterized as a...

Micromachined tunable vertical-cavity surface-emitting lasers

We report a record continuous wavelength tuning range without mode hopping of up to 2.0% in a vertical-cavity surface-emitting laser (VCSEL) utilizing a monolithically-fabricated electrostatically-movable micromirror. A device with a 30 /spl mu/m square top mirror and 4 /spl mu/m diameter active region exhibits a continuous wavelength range of 19.1 nm near 960 nm for 0-18 V tuning bias, a threshold current less than 0.4 mA, and a quantum efficiency of 6.5%. Microsecond wavelength switching is also observed.

25 nm wavelength range tunable vertical cavity lasers

Wavelength tunable lasers are attractive for Wavelength Division Multiplexing (WDM) applications. Conventional WDM relies on fixed wavelength laser arrays, which have temperature-control, system reliability, and manufacturability problems. Because of these shortcomings, wavelength tunable lasers are indispensable elements of such an array since the lasing wavelength of each laser can be set, maintained, or changed to any wavelength within its tuning range. Tunable vertical cavity lasers are optimum for such an array because their short cavity length translates into a single longitudinal mode inside the lasers gain spectrum. This allows continuous tuning without mode hopping. Our approach to tunable VCSEL uses a micromachined suspended deformable membrane that also functions as the top mirror above the semiconductor cavity. Modulating the air gap thickness by applying a bias between the membrane and the semiconductor cavity results in an additional phase shift that effectively modulates the resonance frequency of the VCSEL.

Broadly-tunable narrow-linewidth micromachined laser/photodetector and phototransistor

The key limitation to dense wavelength division multiplexing (WDM) systems is the receiving end since laser linewidths are typically less than 1 /spl Aring/. By reverse biasing the p-i-n diode region, we demonstrated dual functionality of wavelength-tunable vertical-cavity surface-emitting lasers (VCSELs) as wavelength-tunable resonant cavity photodetectors (RCPs) with linewidths less than 2.5 nm. Additionally, we have fabricated wavelength-tunable resonant cavity phototransistors (RCPTs) with linewidths as narrow as 1.7 nm. Wavelength-tunable RCPTs are capable of high quantum efficiency, narrow linewidth, and high-speed operation, making them ideal devices for WDM receivers.

Micromachined tunable vertical cavity lasers as wavelength selective tunable photodetectors

Micromachined tunable VCSELs are particularly useful for wavelength division multiplexing applications because of their large continuous wavelength tuning range without mode-hopping. We have achieved 26 nm single mode continuous wavelength tuning with threshold current density as low as 550 A/cm/sup 2/. By reverse biasing the laser, we can obtain a tunable resonant cavity photodetector with simulated linewidth less than 2 nm. Narrow linewidth tunable photodetectors are particularly useful in extending the wavelength separation between WDM channels beyond those offered by other techniques.

Micromachined tunable optoelectronic devices for spectroscopic applications

Micromachined tunable optoelectronic devices can be used to improve spectroscopic measurements. The standing wave enhancement effect in Fabry-Perot cavities can be used to increase sensitivity. The size and cost of semiconductor micromachined devices make them an attractive alternative to conventional tabletop spectroscopy setups. Recent advances in micromachined tunable optoelectronic devices and their application to spectroscopy are described.