François Balembois

Light-emitting diode pumped luminescent concentrators: a new opportunity for low-cost solid-state lasers

High-power light-emitting diodes (LEDs) today are twice as powerful as four years ago while meantime their price has been divided by 4 making them promising sources for laser pumping. However, their irradiance still falls short by one order of magnitude of what is needed to efficiently pump solid-state lasers. We demonstrate that an LED-pumped Ce:YAG luminescent concentrator (LC) can increase the irradiance of blue LEDs by a factor of 10, with an optical efficiency of 25%, making them much more suitable to pump solid-state lasers. In our demonstration, we used 100xa0Hz pulsed LEDs emitting 190u2009u2009W/cm2 at 430xa0nm to illuminate a Ce:YAG LC, leading to an output irradiance of 1830u2009u2009W/cm2. The LC is used to pump a Nd:YVO4 laser producing 360xa0μJ at 1064xa0nm, corresponding to an optical efficiency of 2.2% with respect to the LC. LED-pumped luminescent concentrators pave the way for high-power, low-cost, solid-state lasers.

Yb:YAG single-crystal fiber amplifiers for picosecond lasers using the divided pulse amplification technique

A two-stage master-oscillator power-amplifier (MOPA) system based on Yb:YAG single-crystal-fiber (SCF) technology and designed for high peak power is studied to significantly increase the pulse energy of a low-power picosecond laser. The first SCF amplifier has been designed for high gain. Using a gain medium optimized in terms of doping concentration and length, an optical gain of 32 dB has been demonstrated. The second amplifier stage designed for high energy using the divided pulse technique allows us to generate a recombined output pulse energy of 2 mJ at 12.5 kHz with a pulse duration of 6 ps corresponding to a peak power of 320 MW. Average powers ranging from 25 to 55 W with repetition rates varying from 12.5 to 500 kHz have been demonstrated.

LED-pumped alexandrite laser oscillator and amplifier

Taking advantage of light-emitting-diode (LED) performance breakthrough driven by the lighting market, we report, to the best of our knowledge, the first LED-pumped chromium-doped crystal laser oscillator and amplifier based on alexandrite crystals (Cr3+:BeAl2O4). We developed a Ce:YAG concentrator as the pumped source, illuminated by blue LEDs that can be easily power scaled. With 2200 LEDs (450xa0nm), the Ce:YAG concentrator can deliver to the gain medium up to 268xa0mJ at 10xa0Hz at 550xa0nm with a irradiance of 8.5u2009u2009kW/cm2. We demonstrate, in oscillator configuration, an LED-pumped alexandrite laser delivering an energy of 2.9xa0mJ at 748xa0nm in free running operation. In the cavity, we measured a double-pass small signal gain of 1.28, which is in good agreement with numerical simulations. As an amplifier, the system demonstrated to boost a CW Ti:sapphire laser by a factor of 4 at 750xa0nm in eight passes with a large tuning range from 710xa0nm to 800xa0nm.

Intense laser emission at 981 nm in an Ytterbium-doped KY(WO 4 ) 2 crystal

We present the first efficient laser emission at the three-level transition at 981 nm in an ytterbium-doped KY(WO4)2 crystal in a microchip configuration. The pump laser is a Ti:sapphire laser emitting at 931 nm. With the maximum pump power, the crystal emits up to 526 mW. We have also demonstrated an intense amplified spontaneous emission at this wavelength, with a maximum power of 320 mW.

First Demonstration of Neodymium True Three Level Laser Emitting at 879 nm

We present the first true three-level-laser based on an Nd-doped crystal. Emission at 879-nm in NdGdVO4 was studied in cw and pulsed regime. SHG was realized to reach blue range at 439.5-nm.

Gain competition in a dual-wavelength Nd:GdVO 4 laser at 1063 nm and 912 nm and intracavity sum-frequency

Simultaneous emissions were demonstrated with a Nd:GdVO4 crystal (912-nm and 1063-nm) and with two crystals: Nd:YLF (1047-nm) and Nd:GdVO4 (912-nm). Blue light was generated by sum-frequency mixing up to 93-mW at 487-nm.

Alexandrite laser LED-pumped via Ce-doped luminescent concentrators

Alexandrite, or chromium-doped chrysoberyl (Cr3+·. BeAl2O4), is known to be the first tunable laser crystal directly diode-pumped at room temperature (1979 Wallin et al [1]). Such lasers are used for medical application (especially dermatology), material processing and Lidar systems. Large absorption coefficients around 410 nm and 590 nm and long room temperature fluorescence lifetime (260 μs) enable traditional flashlamp pumping and red laser diode pumping [2]. Flashlamps being limited in efficiency and red laser diodes having limited performances in terms of output power, it is relevant to consider alternative pumping sources. Recent improvements in LED performance represent a new interesting opportunity for laser pumping. Indeed, LED are more robust, less expensive, extremely less sensitive to the external environment than laser diodes and they are in tremendous expansion with rapid performance improvement thanks to the lightning market. However, their brightness is still few orders of magnitude lower than laser diodes. We recently demonstrated that a luminescent concentrator (LC) can improve the LED intensity by one order of magnitude by overcoming the brightness conservation rule [3]. Here, we propose Alexandrite indirect LED-pumping via Ce-doped LCs.

Contradiction within wave optics and its solution within a particle picture: comment.

An error in the rationale presented in the paper Contradiction within wave optics and its solution within a particle picture by Altmann [Opt. Express 23, 3731 (2015)10.1364/OE.23.003731] is discussed.

First Laser Operation at 899 nm and below in a Diode End-Pumped Nd:YAG

We present the first demonstration of a 899-nm-laser-emission in a Nd:YAG-crystal, on the 4F3/2-4I3/2 transition. 630mW of average power is obtained at 899nm and 100mW at 450nm after an intracavity frequency doubling.

Passively Q-Switched Diode-Pumped Cr4+:YAG/Nd3+:GdVO4 High Repetition Rate Monolithic Microchip Laser

we report on the first passively-Q-switched diode-pumped Nd:GdVO4/Cr:YAG microchip laser. The average power is 400 mW and the pulse length is 1.1 ns at a repetition rate as high as 85 kHz.