Synthesis of a subwavelength-pulse-width spatially modulated array illuminator for 0633 μm

Abstract

We present the design, fabrication, and characterization of a subwavelength-pulse-width spatially modulated diffractive array illuminator for an operating wavelength of 0.633 microm. Electromagnetic and scalar diffraction theories are used to reduce manufacturing difficulties while yielding high diffraction efficiency coupled with low reconstruction error. We employ direct electron beam writing and reactive ion etching to realize a transmission-type three-beam array illuminator in photoresist.

Metalenses at visible wavelengths: past, present, perspectives

“…Initial demonstrations of graded effective‐index artificial‐dielectrics manufactured for visible frequencies by etching quartz, glass and polymer films were disappointing, with measured diffraction efficiencies smaller than those of échelette components . At that time, the design mostly assumed an “adiabatic” effective index gradient, the analogy between local subwavelength gratings and artificial dielectrics was not properly understood, and modeling was challenging.…”

“…Initial demonstrations of graded effective-index artificial-dielectrics manufactured for visible frequencies by etching quartz, glass and polymer films were disappointing, with measured diffraction efficiencies smaller than those oféchelette components [13][14][15][16][17]. At that time, the design mostly assumed an "adiabatic" effective index gradient, the analogy between local subwavelength gratings www.lpr-journal.org LASER & PHOTONICS REVIEWS 1600295 (3 of 11) P. Lalanne and P. Chavel: Metalenses at visible wavelengths: past, present, perspectives…”

<title>Roadmap for micro-optics fabrication</title>

“…Along with these technical hurdles comes an even more daunting task: solve these problems with volume manufacturing in mind! While micro-fabricated photonic bandgap structures have been demonstrated for telecommunications wavelengths [29] and effective medium structure have been demonstrated at visible wavelengths [31][32][33][34], to date these structures have been realized using electron-beam direct writing. E-beam writing enables the fabrication of sub-100 nm features, but the serial nature of the process (and the relatively slow scan speed of the e-beam) makes it unsuitable for volume manufacturing of such devices.…”

“…Common examples of these high-frequency optical structures include waveguide couplers, sub-wavelength anti-reflection structures, resonance structures, gratings for use in distributed feedback (DFB) and distributed Bragg reflector (DBR) laser configurations, wavelength division multiplexing, and many others [25][26][27]. Even more challenging types of optical microstructures have also been proposed and demonstrated, including photonic bandgap structures [28,29] and effective medium structures for a variety of optical functions [30][31][32]. An example of a subwavelength binary lens with 50 nm features and 400 nm depth in fused silica is shown in Figure 2.…”

Diffractive lens fabricated with binary features less than 60 nm

“…To encode n eff ͑x͒ into a binary subwavelength prof ile t͑x͒, we use pulse-width modulation, 4,6,9,10,12 t͑x͒ dX…”