Phosphor Converted Laser Diode Light Source for Endoscopic Diagnostics

Abstract

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A Thermally Robust La3Si6N11:Ce‐in‐Glass Film for High‐Brightness Blue‐Laser‐Driven Solid State Lighting

“…As seen in Figure a, the emission intensity of a typical LSN:Ce‐PiG film (P2G3‐50) increases monotonously as the incident laser power increases from 1.05 to 6.48 W, and it starts to decrease with further increasing the incident power. This reduction can be attributed to the thermal quenching caused by the increasing temperature of the color converter upon the high‐power laser excitation (thermal saturation) . This is also backed up by the red‐shifted emission of the P2G3‐50 with increasing the incident laser power (Figure b).…”

“…Luminescence saturation of the color converter is a serious problem encountered in laser lighting, and it is usually caused by the thermal saturation or the non‐thermal optical saturation . The latter occurs when the decay time is not sufficiently short to convert the absorbed photons.…”

“…Suffering from the high‐density laser irradiation and intense thermal attack, the relevant color converter materials for laser lighting must be carefully selected. Generally, the color converters should meet the following requirements: i) high quantum efficiency (to reduce the heat produced via the non‐radiative relaxation process); ii) small Stokes shift (to decrease the heat generated in the color‐conversion process); iii) high thermal conductivity (to dissipate heat away from the bulk converter effectively); iv) small thermal quenching/degradation (to maintain an acceptable performance at a relatively high temperature); v) short decay time (to avoid the non‐thermal optical saturation caused by the depletion of ground state activators); and vi) proper scattering centers, such as pores, second phases, and grain boundaries (to obtain a high light extraction efficiency and a uniform light distribution) . By considering these requirements, the traditional color converter (i.e., Y 3 Al 5 O 12 :Ce (YAG:Ce) powder + organic resin) used in white LEDs is not suitable for laser lighting anymore owing to the serious thermal damage of the organic resin.…”

High Efficiency Green‐Emitting LuAG:Ce Ceramic Phosphors for Laser Diode Lighting

“…[ 32–36 ] The luminous efficacy (LE) of LuAG:Ce CPs in LD lighting has been greatly enhanced from about 54 to 205 lm W −1 by designing geometric structures and introducing scattering centers. [ 32–37 ]…”

“…[32][33][34][35][36] The luminous efficacy (LE) of LuAG:Ce CPs in LD lighting has been greatly enhanced from about 54 to 205 lm W −1 by designing geometric structures and introducing scattering centers. [32][33][34][35][36][37] However, LuAG CPs are usually sintered higher than 1700 °C, SiO 2 or TEOS is commonly added as sintering aid. [32][33][34] SiO 2 begins to react with the garnets at about 1400 °C, [38] and defects are inevitable due to the size and charge mismatches between Si 4+ and Lu 3+ /Al 3+ .…”