P.E. Britton

Generation of high-power blue light in periodically poled LiNbO3

We report the generation of 450-mW average blue (473-nm) power by frequency doubling of a diode-pumped 946-nm Nd:YAG laser. We achieved pulsed operation at a high repetition rate (~160kHz) by driving the relaxation oscillations of the laser. A 40% conversion efficiency to the second harmonic was obtained in a single-pass, extracavity, first-order, quasi-phase-matched process in which periodically poled lithium niobate (period 4.5microm , thickness 0.5mm , and length 15mm) at 140 degrees C was used. The resulting high-power blue beam was circular in profile and nearly diffraction limited, indicating that photorefractive effects do not appear to limit device performance.

Highly efficient second-harmonic and sum-frequency generation of nanosecond pulses in a cascaded erbium-doped fiber:periodically poled lithium niobate source.

By combining erbium-doped fiber sources based on a large mode-area design and periodically poled lithium niobate, we have obtained single-pass conversion efficiencies of as much as 83% (energy efficiency) for second-harmonic generation into the near IR (768 nm) and of 34% for sum-frequency generation into the green (512 nm) for nanosecond pulses, using first-order quasi-phase matching. Pulse energies in excess of 80microJ of second harmonic have been obtained from systems pumped by a single laser diode.

Optical parametric oscillation in periodically poled lithium niobate driven by a diode-pumped Q-switched erbium fiber laser.

We describe what is to our knowledge the first nanosecond periodically poled lithium niobate (PPLN) optical parametric oscillator (OPO) driven by a fiber laser. The source was frequency doubled by a PPLN sample before pumping a second, 20-mm-long, PPLN crystal. The OPO threshold was <10muJ, with pump depletions of as much as 45% and a tunable signal range of 945-1450 nm (1690-4450-nm idler range). We demonstrated 130-nm signal tuning by varying the pump wavelength and doubling crystals temperature. Also, we achieved 15-nm tuning with all crystals at a constant temperature. The results demonstrate the potential of the fiber laser:PPLN combination for practical, versatile, and tunable sources.

Wavelength-tunable high-power picosecond pulses from a fiber-pumped diode-seeded high-gain parametric amplifier

We describe a high-gain optical parametric amplifier (OPA) and optical parametric generator (OPG) system pumped by a fiber chirped-pulse amplification source based on novel large-mode-area fiber components. 45-nJ OPG thresholds and 34% pump-signal conversion efficiencies are obtained for ~4-ps pulses. OPA gains in excess of 75 dB and pump-signal conversion efficiencies of ~39% (external) are demonstrated. Furthermore, we show that injection seeding of such high-gain parametric devices by use of a low-power continuous-wave beam results in high-power (>18-kW) picosecond pulses with a time-bandwidth produce of ~0.65, some ten times less than from a free-running OPG. Using such an approach, we obtain 2.7-ps 50-nJ pulses at 1.310 mum .

Parametric oscillator directly pumped by a 1.55-µm erbium-fiber laser

We report what is believed to be the first demonstration of an optical parametric oscillator directly pumped by the 1.55-mum output of an erbium-doped fiber laser. The oscillator, based on periodically poled lithium niobate, produced 8-muJ idler output near 3.8 mum at a 500-Hz repetition rate when it was pumped with 100-muJ 60-ns pulses at 1.55 mum . Temperature tuning of the 50-mm-long PPLN crystal gave signal and idler ranges of 2.55 to 2.7 mum and 3.65 to 3.96 mum , respectively, limited by mirror reflectivity. A signal-tuning range of 40 nm was observed for 13.5 nm of pump tuning with a fixed grating period and temperature. The optical parameter oscillator could be operated at low temperature with no sign of photorefractive damage.

A parametric oscillator directly pumped by a 1.55 micron erbium fibre laser

We report what is believed to be the first demonstration of an optical parametric oscillator directly pumped by the 1.55-mum output of an erbium-doped fiber laser. The oscillator, based on periodically poled lithium niobate, produced 8-muJ idler output near 3.8 mum at a 500-Hz repetition rate when it was pumped with 100-muJ 60-ns pulses at 1.55 mum . Temperature tuning of the 50-mm-long PPLN crystal gave signal and idler ranges of 2.55 to 2.7 mum and 3.65 to 3.96 mum , respectively, limited by mirror reflectivity. A signal-tuning range of 40 nm was observed for 13.5 nm of pump tuning with a fixed grating period and temperature. The optical parameter oscillator could be operated at low temperature with no sign of photorefractive damage.

Red and blue light generation by frequency doubling and tripling in periodically poled LiNbO/sub 3/

Periodically poled LiNbO/sub 3/ (PPLN), with its high optical nonlinearity and noncritical phase matching, is an attractive nonlinear material for generating high-power visible output via frequency upconversion of existing infrared sources. In this work, we demonstrate second- and third-harmonic generation of an Nd:YAG laser (1320 nm) to produce red (660 nm) and blue (440 nm) wavelengths with high spatial beam quality in a simple single-pass arrangement. Samples of PPLN were prepared with the electric-field poling technique. The results demonstrate the capability of sum-frequency generation, even in a third-order interaction, to generate significant powers of blue (440 nm) light in PPLN. Additionally, results show that photorefractive effects can be successfully eliminated in undoped LiNbO/sub 3/ at this short wavelength. Provision of antireflection coatings for optics and crystals and optimization of beam overlap in the frequency-mixing process should all offer a significant improvement in performance.

PPLN based picosecond Parametric Generator driven by an all-fibre erbium doped fibre amplifier system

Presented is a compact periodically poled lithium niobate based picosecond optical parametric generator, pumped by a truly all-fibre chirped pulsed amplification system. This sources high powers and frequency doubling allowed efficient energy conversion, (43%).

PPLN Based Picosecond Parametic Generator Driven by an All-Fibre Erbium Doped Fibre Amplifier System

It 13 Q D k I I l i d ? very useful to be able to generate a wide range of mffcrent wwelenghs fmm rlic same Fmlurncr ~nvers lon dwcc. In this repon preli~narr work IS dcscnbed on the development u f B KTP cavmly that can operate as crthcr an optteal pa-etnc os~il lator or as a Ramm o~cil lator Swuhmg bLnvccn the different madci ofoprrrbon 1s awmplabcd by srmply mmmg the polari~znun of the p-Q beam A mdr locka l and Qwirched NdYAG laem operatmg at 1 064 w is usid to rpchronoosly pump thc KTP miitv The mulrhcked pulrcr havo il duration of 143 PE, are separated b? I3 ni md u c mitamed within a Q-swtchsd ciirelope of duration ,0,