Abstract: A light guide plate (30) has a light incident surface (305) for receiving light, a light emitting surface (301) for emitting light, a bottom surface (303) opposite to the light emitting surface, and side surfaces (307, 309, 311). A subwavelength grating (302) is formed on the light incident surface for diffracting the light. The subwavelength grating is a zeroth-order grating which covers a wide wavelength band and diffracts the light into zeroth-order waves. So that the light guide plate has a high light utilization efficiency and yields high uniformity of outgoing light.

Abstract: The present invention provides core technologies necessary for a portable, low cost, thermal-regulating LED-based handheld fluorometer. The regulated fluorometer is based on a low thermal mass infrared heater, and an orthogonal geometry LED based filter fluorometer. Power is supplied through an external power supply and data is collected in real-time through standard serial interfaces of personal computers or personal digital assistants. Thermal regulation is automatically maintained using temperature sensor feedback control. Optical excitation relies on LED light source(s) and optical detection is through an adjustable integrating photodetector. Such a handheld system can allow applications requiring temperature sensitive photometric measurements for real time analyte detection to be performed in the field.