SUBWAVELENGTH-RESONANT-GRATING MIRROR AND CAVITY FOR SINGLE-MODE, SUB-PM-LINEWIDTH, UV (220-240 NM) LASER
Abstract
Statement of Work Task 1. Sub-pm-Linewidth, Subwavelength-Resonant-Grating (SPL-SRG) Mirror. Explore the designs (analytical and simulations), fabrication and testing of SPL-SRG mirror for 220 nm wavelength application. The SRG’s performance (the resonant wavelength, linewidth, and reflectivity) will be investigated and optimized as a function of the SRG’s materials and structures (the pitch, height and duty cycle of the grating) as well as the fabrication quality (feature dimension controls, grating edge roughness, and defects). Initially, the SRG pitch (i.e. period) is 135 nm and the material systems will be Al2O3/quartz and Al2O3/CaF2. Nanoimprint with our existing mold will be used. Sub-10 pm linewidth for the SRG and for an external cavity laser using SRG are expected. Task 2. Nanoplasmonic Photo-Hole-Generator (NPHG). Explore the design, fabrication and characterization of high-efficiency plasmonic-enhanced photo-hole generator (NPHG). Several different NPHG structures will be explored. The most promising one is the disk-and-hole-plane (DHP) structure in ZnO. A standalone NPHG will be tested, and later will be integrated with an AlN quantum well structure to further test hole injections. The efficiency in light absorption, photogeneration of electron-hole-pairs and hole transport in NPHG will be studied and optimized. Effects of plasmonic material and nanostructures as well as the band alignment and doping in ZnO will be studied and optimized. Approach The most significant innovation for the overall goal of the proposed research is the new UV laser structure, termed “Sub-pm-linewidth photo-assisted electrical injection Laser” (SPEL). Two of the most significant innovative components in the new laser, which are the focus of this proposal, are (a) single-mode subwavelength resonant grating mirror (SGR) -- a novel single-mode sub-pm-linewidth external cavity that uses a single-mode sub-pm-linewidth subwavelength-resonant-grating as a mirror, where the lasing peak wavelength is entirely determined by the SRG mirror, not by the cavity length, and the lasing linewidth will be determined by the linewidth of either the SRG or the external cavity or their interplay; and (b) nanoplasmonic photo-hole generator (NPHG) – that uses nanoplasmonic structure to achieve high-efficiency light absorption and photo-hole-generation in ZnO by a 365 nm wavelength light radiation and serves as a hole injector when placed next the quantum well, delivering sufficient hole current for lasing. Specifically, SPEL comprises a compact external cavity (<5 mm long) with special edge emitting laser chip as the gain medium, one broad-band total-reflectivity mirror directly on one laserchip’s facet, and one ultra-narrow-band wavelength-selecting output mirror, SRG, near the chip’s other facet (antireflection coated) and coupled to the facet by optics (e.g. a ball lens). The special laser chip, AlGaN multi-quantum-well on AlN substrate, has the electrons injected directly by electrical current and the holes injected through the NPHG (made in a thin ZnO layer and the plasmonic structure also acts as the p-side contact sinking the electrons) which is placed next to the lasing quantum wells to replace p-AlGaN hole transport layer. Objective A goal of the DARPA LUSTER program is to develop a new UV (220-240 nm) laser structure, subpm-linewidth photo-assisted electrical-injection laser (SPEL), that is expected to be compact, high power, efficient, and single mode with sub-10 pm linewidth. One key component is single-mode subwavelength-resonant grating mirror (SGR mirror). The objective of this proposed research is to develop the SGR mirror, which, when integrated with the SPEL’s external cavity, gives a single lasing mode with sub-10 pm linewidth. The proposed research will focus on the key component rather than building the entire new SPEL laser system, and will work multiple teams who are working on DARPA LUSTER program.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512736
Entities
People
- Stephen Y. Chou
Organizations
- Office of Naval Research
- Trustees of Princeton University
- United States Navy