Steve Lecomte

Compact Nd:YVO/sub 4/ lasers with pulse repetition rates up to 160 GHz

We present a comprehensive study on multigigahertz repetition rate Nd:YVO/sub 4/ lasers, passively mode-locked with semiconductor saturable absorber mirrors. A brief review of Q-switching instabilities with special emphasis on high repetition rate is given. We then present basic design guidelines, and experimentally show that one can push the pulse repetition rate of a Nd: YVO/sub 4/ laser up to 157 GHz, reaching the fundamental limit to the repetition rate which is given by the pulse duration and thus by the amplification bandwidth. We also demonstrate an air-cooled diode-pumped 10-GHz Nd: YVO/sub 4/ laser with 2.1-W average output power and 13% electrical-to-optical efficiency, showing the potential of solid-state lasers generating multiwatt, multigigahertz pulse trains with high efficiency.

Self-referenceable frequency comb from a gigahertz diode-pumped solid-state laser

We present carrier envelope offset (CEO) frequency detection of a diode-pumped Yb:KGW (ytterbium-doped potassium gadolinium tungstate) laser with a repetition rate of 1 GHz. The SESAM-soliton-modelocked laser delivers 2.2-W average power in 290-fs pulses. This corresponds to a peak power of 6.7 kW and the optical-to-optical efficiency is 38%. With a passive pulse compression the duration is reduced to 100 fs at an average power of 1.1 W. Coherent supercontinuum (SC) generation in a highly nonlinear photonic crystal fiber (PCF) is achieved without additional amplification. Furthermore we have demonstrated that pulse compression towards lower soliton orders of approximately 10 was required for coherent SC generation and CEO detection. Additional numerical simulations further confirm these experimental results.

Picosecond pulse sources with multi-GHz repetition rates and high output power

We review and compare several recently introduced approaches for the generation of picosecond pulse trains with multi-GHz repetition rates and relatively high average output power (up to several watts). Specifically, we consider passively mode-locked lasers with different gain media (Nd:YVO4, Er:Yb:glass, and surface-emitting semiconductor structures) as well as optical parametric oscillators.

Reversible optical structuring of polymer waveguides doped with photochromic molecules

We show that polymeric films doped with the photochromic molecule 1,8a-dihydro-2(4-iodophenyl)-1,1-azulenedicarbonitrile can be reversibly structured by light. We discuss the relevant material properties of the photochromic molecule in solution as well as in polymer films and demonstrate light-induced waveguides at the telecommunication wavelength of 1.313 μm.

Optical parametric oscillator with a 10-GHz repetition rate and 100-mW average output power in the spectral region near 1.5 µm

We demonstrate a synchronously pumped optical parametric oscillator that emits picosecond pulses at an ~1.55-mum wavelength with a repetition rate as a high as 10 GHz and as much as 100 mW of average power. It is pumped with a diode-pumped passively mode-locked 10-GHz Nd:YVO(4) laser. Because of its high repetition rate and its potential for ultrabroad tunability, this kind of system is useful for telecom applications. It should be scalable to 40 GHz and higher as required for future telecom networks.

Compact 10-GHz Nd:GdVO 4 laser with 0.5-W average output power and low timing jitter

We demonstrate a compact, diode-pumped Nd:GdVO4 laser with a repetition rate of 9.66 GHz and 0.5-W average output power. The laser is passively mode locked with a semiconductor saturable absorber mirror (SESAM), yielding 12-ps-long sech2-shaped pulses. For synchronization of the pulse train to an external reference clock, the SESAM is mounted on a piezoelectric transducer. With an electronic feedback loop of only a few kilohertz loop bandwidth we achieved a rms timing jitter of 146 fs (integrated from 10 Hz to 10 MHz). This is an upper limit because it is mostly limited by the measurement system. The laser setup with a simple linear cavity has a footprint of only 130 mm x 30 mm.

Sub-100 attosecond timing jitter from low-noise passively mode-locked solid-state laser at telecom wavelength

We report on the ultralow timing jitter of the 100 MHz pulse trains generated by two identical passively mode-locked diode-pumped solid-state lasers (DPSSLs) emitting at 1556 nm. Ultralow timing jitter of 83 as (integrated from 10 kHz to 50 MHz) for one laser has been measured with a balanced optical cross-correlator as timing discriminator. Extremely low intensity noise has been measured as well. Several measurement techniques have been used and show similar jitter results. Different possible noise sources have been theoretically investigated and compared to the measured jitter power spectral density. It is found that although the measured integrated jitter is quite low, it is still significantly above the quantum limit in the considered frequency span. Therefore, there is a substantial potential for technical improvements that could make passively mode-locked DPSSL outperform fiber lasers as source of microwaves with low phase noise.

Diode-pumped passively mode-locked Nd:YVO/sub 4/ lasers with 40-GHz repetition rate

We present two different diode-pumped passively mode-locked Nd:YVO/sub 4/ lasers with a repetition rate of 40 GHz. This is the highest repetition rate demonstrated so far with diode-pumped 1-/spl mu/m solid-state lasers. The first laser design allows short pulses of 2.7-ps duration whereas the second laser design is optimized for high average output power of up to 288 mW. We compare both design approaches and show that there is a tradeoff between output power and pulse duration.

Photoinduced reversible optical gratings in photochromic diarylethene-doped polymeric thin films

We report on our investigation of the potential for all-optical reversible photostructuring of the photochromic molecule 1,2-bis(2-methylbenzo[b]thiophen-3-yl)perfluorocyclopentene (BFCP). The light-induced isomerization of BFCP was studied in solution as well as in polymeric thin films. The absorption change that is due to the photochromic reaction of BFCP was determined by conventional spectroscopic measurements. The absolute values of the refractive indices of doped polymer films were measured by the waveguide grating coupling technique for the two states of the photochromic molecule. The dynamics of the reactions and the light-induced refractive-index changes Δn of doped polymer samples were investigated in holographic grating experiments. Changes of as much as Δn=(3.5±0.5)×10-4 were obtained at 806 nm for 41.16-wt. % doping. Finally, a modified two-beam coupling experiment permitted the separation of absorption and refractive-index contributions to the grating buildup and the determination of the phase shifts of these gratings with respect to the intensity grating.

Synchronously pumped optical parametric oscillator with a repetition rate of 81.8 GHz

We present a singly resonant synchronously pumped optical parametric oscillator with a record-high pulse repetition rate of 81.8 GHz. It generates up to 0.9 W of signal average output power at a wavelength of 1569.7 nm. The pulses have a duration of 2.4 ps and are nearly transform-limited. The device is wavelength tunable from 1541.4 to 1592.2 nm. The tuning range could be easily extended by the use of a multiperiod periodically poled LiNbO/sub 3/ crystal.