University of California

Christopher Chase

Connie J Chang-Hasnain

Forrest G Sedgwick

Vadim Karagodsky

Fanglu Lu

Weijian Yang

Planar lenses and reflectors are described comprising subwavelength high-contrast gratings (HCG) having high index of refraction grating elements spaced apart from one another in straight and/or curved segments and surrounded by low index material. The high-contrast grating is configured to receive an incident wave which excites multiple modes within the high-contrast grating and is focused for reflection and/or transmission by said high contrast grating. The width of the high contrast grating bars vary along a distribution direction of the grating bars which is perpendicular to the length of the grating bars and/or varies along the length of one or more grating bars to focus said reflection and/or transmission. The HCG is configured to provide double focusing, whose use is exemplified within a vertical cavity surface emitting laser (VCSEL) structure using focusing HCG structures for both the top and bottom mirrors.

Planar, high NA, low loss transmitting or reflecting lenses using sub-wavelength high contrast grating

A saturable absorber (SA) based on a high-contrast grating (HCG) having a buried layer of quantum structures for absorption, and which is particularly well suited for use in a mode-locked application. The HCG-SA provides three times the bandwidth compared with traditional DBR structures, while exhibiting a lower saturation fluence due to the field enhancement inside the grating. Varying grating bar width over one or two axis provides lensing effects on the optical output, while chirping of the period and duty cycle changes optical phase relationships. Novel VCSEL embodiments with external or internal cavities are described using the HCG-SA.

High contrast grating based saturable absorber for mode-locked lasers and its applications in passively mode-locked vertical-cavity surface-emitting lasers

Enhanced reflectivity High-Contrast Gratings are described which operate in different medium. An HCG is described with a deep/buried metallization layer separated at a distance of least three to four grating thicknesses from the grating. Reflective bandwidth of the HCG is substantially increased, such as by a factor or five, by inclusion of the deep/buried metallization layer. An HCG is described which provides high reflectivity, even when embedded into materials of a moderate to high index of refraction, such as semiconductor material. Vertical cavity surface emitting laser embodiments are described which utilize these reflectivity enhancements, and preferably utilize HCG reflectors for top and/or bottom mirrors.

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Kensington, CA, United States of America

Christopher Chase