Single cubic phase Yb2O3:Er3+ phosphors have been synthesized via solid state reaction technique and characterized by X‐ray diffraction (XRD) and Field emission scanning electron microscopy (FE‐SEM) analysis. An unusual continuum broad band white colour upconversion (UC) emission has been observed under 980 nm continuous wave (CW) near infrared (NIR) laser diode excitation. Interestingly, the phosphor shows characteristic erbium ion transitions at low pump power, but at high pump power heat associated continuum broad band emission was realized. The continuum broad band emission was explained on the basis of energy level diagram, laser induced pump power dependence and blackbody radiation theory. The heat associated/incandescence‐like light is originated due to heating induced by the nonradiative relaxation followed by sensitization (Yb → Er) and Yb−Yb dimer formation. The synthesized phosphor emits effective broad band white colour emission under high pump power and colour co‐ordinates (white colour: 0.34, 0.32) were located in the chromaticity diagram. Intrinsic optical bistability (IOB) behavior shows the hysteresis‐like loop originated upon variation in the laser pump power. The observed high temperature at point of irradiation of the prepared nanocrystalline phosphor is about ∼ 2442 K at 1430 mW, which is high as compare to tungsten bulb (2400 K for 100 W). The developed phosphors can be useful in white light production, solar cell efficiency enhancement, switchable bistable and as light to heat converter.

Wavelength (nm)CTuAA2 Fig. 2 Real-time measurement of water vapor absorption profile (16 m atmospheric path) with use of a fiber grating external cavity laser diode transmitter. 0.6 -L Q) 0.5 0 s n 0.4 -$ 0 . 3 0. .-!U 0 0.2 Y g 0.1 n 0 Time (1 Lsldiv) CTuAA2 Fig. 3 Detected optical output pulse from a 935 nm wavelength discrete component semiconductor MOPA laser transmitter. 10 kHz repetition rate, 2 p,s pulse width current modulation was applied to the flared amplifier.with a 1-W fiber-coupled 808-nm diode laser, it produced a 30-kHz train of singlefrequency, TEM,, pulses, with a pulse width of 11 ns (FWHM) and a pulse energy of 0.6 11.7. Overlaps between appropriate water vapor absorption lines and gain in other Nd3+ doped materials have been identified, but demonstration of output wavelength tuning to a water vapor line is still needed.In approach (3), a Sensors Unlimited Inc. Model SU 935 CD FP 50 mW Fabry-Perot InGaAs laser diode was coupled to a 3M Inc. fiber optic grating with a 935.4 nm center wavelength at 25 C, a 0.1 nm bandpass, and 7% reflectivity. The laser and fiber grating were temperature tuned to the water vapor absorption line at 935.7 nm. Figure 2 shows a real time measurement of the water vapor absorption line profile over a 16 meter free space optical path using the fiber grating external cavity laser as the transmitter.In a high power demonstration, Figure 3 shows the detected pulsed output from a semiconductor MOPA laser consisting of an external cavity grating master oscillator and a modulated SDL Inc. Model 8630-E InGaAs flared amplifier.We will present further experimental data on these transmitters and their use for atmospheric water vapor measurements. Differential absorption lidar (DIAL) is a wellestablished technique for measurement of atmospheric water vapor and other species. However, its application has been constrained by the complexity and limitations of available narrow-linewidth, high spectral purity lasers. We have previously reported' the characterization of an optical parametric oscillator (OPO) and demonstrated that it is an attractive source for DIAL measurement. This source has now been incorporated into a DIAL system for measuring water vapor and predicting its effect on radar propagation. Here we present the DIAL system design, water vapor profile measurements with comparison to radiosonde data, and an assessment ofthe system capabilities.The on-line transmitter is a commercial OPO (Continuum Mirage 800) that uses a KTP oscillator and two Tisapphire amplifiers. The OPO system produces 10 Hz, 20 mJ single frequency (Am = 0.013 cm-') output at the on-line wavelength of 732.29 nm (U = 13655.817 cm-').An Alexandrite laser, line-narrowed by a three plate birefringent filter, is the off-line source. Return signal is collected by a 20" Dall-Kirkham telescope and a mobile scanning mirror. The detection system includes two PMTs that collect near (2 km) and far field (7.5 km) signals. A PC-based lidar control module performs the firing of the lasers, and data acquisition with t...