Ultra-broadband optical parametric chirped-pulse amplification using an Yb: LiYF(4) chirped-pulse amplification pump laser

Broadly tunable (993-1110 nm) Yb:YLF laser

We have investigated room-temperature continuous-wave (cw) lasing performance of Yb:YLF oscillators in detail using rod-type crystals with low Yb-doping (2%). The laser is pumped by a low-cost, high brightness, 10 W, 960 nm single-emitter multimode diode. Laser performance is acquired in both E//a and E//c configurations, using 12 different output couplers with transmission ranging from 0.015% to 70%. We have estimated the passive loss of the Yb:YLF crystal as 0.06% per cm, corresponding to an impressive crystal figure of merit above 4000. The low-doping level not only reduces the system losses but also minimizes the thermal load as the low doped crystals enable distribution of heat load in a greater volume. Using the advantages of lower loss and improved thermal behavior, we have achieved cw output power above 4 W, cw slope efficiencies up to 78%, and a record cw tuning range covering the 993-1110 nm region (117 nm). The output power performance achieved in this initial work is limited by the available pump power, and future room-temperature Yb:YLF systems have the potential to produce higher output power levels.

Regenerative terahertz wave parametric amplifier based on four-wave mixing in asynchronously pumped graphene oxide integrated TOPAS

A widely tunable regenerative terahertz parametric amplifier is proposed based on degenerate four-wave mixing in an asynchronously pumped highly nonlinear medium. To enhance the Kerr nonlinearity, a hybrid structure of cyclic olefin co/polymer (COC/P) TOPAS integrated by a graphene oxide film is utilized as the gain medium and embedded into a cavity. A low-power terahertz seed wave is injected inside the cavity and sequentially pumped by four asynchronous coupled beams of identical powers. Our results reveal that the output power, the tuning frequency range and the power conversion efficiency of terahertz waves could be considerably improved in the proposed design. Terahertz waves with maximum peak power of 641 W, the accumulated conversion efficiency of 3.8% and amplification gain of 320.5 are obtained at a frequency of 9.61 THz, which could be tuned over a range of 1.17 - 19.736 THz.

Mode-locked Cr:LiSAF laser far off the gain peak: tunable sub-200-fs pulses near 1 µm

We report, to the best of our knowledge, the first mode-locking results of a Cr:LiSAF laser near the 1 µm region. The system is pumped only by a single 1.1 W high-brightness tapered diode laser at 675 nm. A semiconductor saturable absorber mirror (SESAM) with a modulation depth of 1.5% and non-saturable losses below 0.5% was used for mode-locking. Once mode-locked, the Cr:LiSAF laser produced almost-transform-limited sub-200-fs pulses with up to 12.5 mW of average power at a repetition rate of 150 MHz. Using an intracavity birefringent filter, the central wavelength of the pulses could be smoothly tuned in the 1000-1020 nm range. Via careful dispersion optimization, pulse widths could be reduced down to the 110-fs level. The performance in this initial study was limited by the design parameters of the SESAM used, especially its passive losses and could be improved with an optimized SESAM design.

Generation of few-cycle infrared pulses from a degenerate dual-pump OPCPA

A degenerate dual-pump optical parametric chirped-pulse amplifier (OPCPA) for generation of few-cycle intense pulses centered at 1.6 μm is theoretically investigated. By adding the optimized linear chirp to the two pump pulses from Ti:sapphire source and carefully adjusting the delays between the two pumps and seed, the long- and short-wavelength components of the seed pulse are efficiently amplified during the parametric process. Our simulations show that a broadband spectrum spanning from 1.3 μm to 2.1 μm is attained with a conversion efficiency of 22.6%. Signal pulse with a near transform-limited (TL) duration of 10.1 fs can be achieved by simply removing the linear chirp from the output signal. Besides, the compressed signal beam manifests good quality both spectrally and temporally, which allows tightly focusing the signal beam for further use.

Wide-time-range spectral-shearing interferometry

A long-time-range spectral-shearing interferometry has been demonstrated by frequency mixing with two-color monochromatic fields. Strongly chirped pulses with quadratic and cubic phase distortion have been characterized. A linearly chirped pulse having 2.2 ps (full duration of 6 ps) has been measured with a coaxial two-color field generated by a narrow-gap passive etalon. Substantial extensions in the time range can be expected with a highly coherent two-color source, i.e., frequency stabilized lasers, or two longitudinal modes in the frequency comb.

Controlling the phase matching conditions of optical parametric chirped-pulse amplification using partially deuterated KDP

Using a partially deuterated KDP crystal for an optical parametric amplifier, we demonstrated ultrabroadband optical parametric chirped-pulse amplification of more than 250 nm bandwidth at a center wavelength of 1050 nm. We numerically show how to control the broadband phase matching conditions at different wavelengths to match center wavelengths of suitable broadband seed sources by adjusting the deuteration level in partially deuterated KDP.