Sheng-Han Tu

High efficiency pocket-size projector with a compact projection lens and a light emitting diode-based light source system

We present a light emitting diode (LED)-based ultramini digital micromirror device projector with a size of 75 mm x 67 mm x 42 mm and a weight of 338 g. The LED illuminator inside this projector makes it possible to achieve a volume of 18 cm(3) by using a dichroic filter and a collimating lens. The illumination system consists of high uniformity of 93% through a microlens array as a homogenizer. A total internal reflection prism is also used to reduce the size of both the illumination system and the telecentric projection lens. A projection lens system with an ultrasmall track of 42 mm, including a high modulation transfer function value of 0.4 at 46.2 line pairs/mm, an optical distortion of only 0.25 %, and a television distortion of 0.01%, is designed. Through the above superior specification, we can produce a 20 in. (51 cm) color display comparable in brightness to a laptop with a contrast of 3700:1. The device is compact and suitable for personal use.

Integration of Non-Lambertian LED and Reflective Optical Element as Efficient Street Lamp

A cost effective, high throughput, and high yield method for the increase of street lamp potency was proposed in this paper. We integrated the imprinting technology and the reflective optical element to obtain a street lamp with high illumination efficiency and without glare effect. The imprinting technique can increase the light extraction efficiency and modulate the intensity distribution in the chip level. The non-Lambertian light source was achieved by using imprinting technique. The compact reflective optical element was added to efficiently suppress the emitting light intensity with small emitting angle for the uniform of illumination intensity and excluded the light with high emitting angle for the prevention of glare. Compared to the conventional street lamp, the novel design has 40% enhancement in illumination intensity, the uniform illumination and the glare effect elimination.

Polarization dependent light extraction of a GaN light emitting diode using dark field angle-resolved photoluminescence spectrometry

In this paper, the polarization dependent optical properties of GaN surface relief grating are investigated using dark field angle-resolved photoluminescence (ARPL) spectrometer. The light extraction efficiency with the transverse electric (TE) and transverse magnetic (TM) pumping source represents a TE polarized dominated property. It is found that the TE and TM waveguide modes cannot be simultaneously coupled out, therefore light extraction is polarization dependent. The ARPL spectrum also reveals that the extraction efficiency is relatively high as the dispersion line of the waveguide mode is coincident with the folded free-photon dispersion of the 1D GaN grating.

Silicon-based micro and subwavelength optical elements and applications

In this paper, silicon-based micro and subwavelength optical elements based on a free-standing silicon nitride (SiNx) membrane are achieved. These elements, including gratings, microlenses, and holographic optical elements (HOEs), are designed and used within the visible and infrared regions. These devices can be used as collimators, reflectors, and wavelength-dependent filters with advantages of simple structure, high efficiency and feasibility to integrate with other elements into a micro-system chip. In order to demonstrate the advantage of micro-optics of free-standing SiNx membrane type in integration, a miniaturized optical pickup head module based on a stacked micro-optical system is developed. This module consisted of a laser diode, a reflector, a grating, a holographic optical element, and some aspherical Fresnel lenses. The novel microoptical system can overcome the problems encountered in other microoptical systems such as off-axis aberration, lower optical efficiency or durability, integration and even in fabrication. A focal spot with a FWHM diameter of 3.3 μm is obtained while the diffraction limited full-width at half-maximum (FWHM) is 0.7 μm. To extend the advantage of micro-optics of free-standing SiNx membrane, the subwavelength optical elements base on guided-mode resonance is also developed. With various Si-based structures, the filter possesses numerous properties such as variable bandwidths, low sideband, flattop, and etc. They are also applied as biosensors to detect the hybridization process of bio reaction for their high sensitivity. The results show that micro and subwavelength optical elements fabricated on Si-based material will be a candidate for emerging silicon micro-photonics.

Demonstration of a simplified optical mouse lighting module by integrating the non-Lambertian LED chip and the free-form surface

A cost-effective, high-throughput, and high-yield method for the efficiency enhancement of an optical mouse lighting module is proposed. We integrated imprinting technology and free-form surface design to obtain a lighting module with high illumination efficiency and uniform intensity distribution. The imprinting technique can increase the light extraction efficiency and modulate the intensity distribution of light-emitting diodes. A modulated light source was utilized to add a compact free-form surface element to create a lighting module with 95% uniformity and 80% optical efficiency.

Optical properties of light emitting diodes with a cascading plasmonic grating

In this paper, the polarization dependent optical properties of InGaN/GaN multi-quantum wells (MQWs) LED with cascading plasmonic gratings are investigated using an angle-resolved photoluminescence (ARPL) spectrometer. The plasmonic gratings consist of two Ag gratings with a half-pitch displacement. The ARPL spectra of the TE-TM state present a broadband emission with resonance dips occasioned by the SP resonance while the TM-TE state presents resonance peaks with low sideband emission. The resonance properties can be tuned by modifying the geometric parameters of the plasmonic grating. The ARPL spectrum of the LED sample with pure GaN 1D grating is also measured and discussed. The investigated plasmonics LED represents resonance optical properties different from the conventional surface relief LED, which can be used in special applications.

60.3: A Novel Backlight System with High On-axis Luminance and Small Viewing Angle

We introduce a novel backlight module, which consists of a hybrid light guide plate (HLGP) and a brightness enhancement film (BEF). The HLGP comprises the functions of conventional light guide plate, reflector, and a BEF. The HLGP allows one-dimensional light to be collimated. We add an additional BEF above the HLGP, and let the crossed-dimension light to be collimated. Comparing with the conventional edge-lit backlight module, the total flux can improve 1.5 times and the on-axis luminance can improve 4.0 times by using the novel backlight module.