Characterization of a high efficiency, ultrashort pulse shaper incorporating a reflective 4096-element spatial light modulator

We demonstrate pulse shaping via arbitrary phase modulation with a reflective, 1 × 4096 element, liquid crystal spatial light modulator (SLM). The unique construction of this device provides a very high efficiency when the device is used for phase modulation only in a prism based pulse shaper, namely 85%. We also present a single shot characterization of the SLM in the spatial domain and a single shot characterization of the pulse shaper in the spectral domain. These characterization methods provide a detailed picture of how the SLM modifies the spectral phase of an ultrashort pulse.     

Direct space-to-time pulse shaper with reflective arrayed waveguide gratings and phase masks

We demonstrate for what we believe to be the first time the generation of sequences of ultrafast optical pulses by phase modulation in a direct space-to-time pulse shaper. The pulse shaper is based on the combination of a reflective arrayed waveguide grating multiplexer and an external reflector. The spatial modulation of the phase was obtained by fabricating corrugated patterns on the external reflector. We demonstrate that pulse sequences with different repetition rates can be obtained by changing the period in the patterned mask.     

Pulse shaper assisted short laser pulse characterization

We demonstrate that a pulse shaper is able to simultaneously act as an optical waveform generator and a short pulse characterization device when combined with an appropriate nonlinear element. We present autocorrelation measurements and their frequency resolved counterparts. We show that control over the carrier envelope phase allows continuous tuning between an intensity-like and an interferometric autocorrelation. By changing the transfer function other measurement techniques, for example STRUT, are easily realized without any modification of the optical setup. PACS 42.65.Re; 42.30.Lr; 42.30.Rx     

Photonic generation of arbitrary waveforms based on incoherent wavelength-to-time mapping

We demonstrate experimentally a radio frequency arbitrary waveform generator using the incoherent wavelengthto-time mapping technique.The system is implemented by amplitude modulation of a broadband optical resource whose spectrum is reshaped by a programmable optical pulse shaper and transmitted over a single mode fiber link.The shape of the generated waveform is controlled by the optical pulse shaper,and the fiber link introduces a certain group velocity delay to implement wavelength-to-time mapping.Assisted by the flexible optical pulse shaper,we obtain different shapes of optical waveforms,such as rectangle,triangle,and sawtooth waveforms.Furthermore,we also demonstrate ultra-wideband generation,such as Gaussian monocycle,doublet,and triplet waveforms,using the incoherent technique.     

Pulse shaper in a loop: demonstration of cascadable ultrafast all-optical code translation

We experimentally demonstrate repetitive M-ary spectral phase pulse shaping by placing a programmable pulse shaper driven by a 10-GHz source in a closed loop. This permits generation of encoded and decoded signals in the same apparatus by forming a closed loop to circulate a part of the output back into the pulse shaper. As a result, a series of M - 1 distinct encoded waveforms is sequentially generated, followed by generation of a properly decoded pulse.     

Chirp control in the direct space-to-time pulse shaper

The dispersion properties of the direct space-to-time pulse shaper are investigated for the first time to our knowledge. We demonstrate that phase-front curvature of the input spatial profile leads to a chirp in the output temporal waveform, which one can compensate for by varying the separation between the pulse-shaping lens and slit. Furthermore, the output intensity profile remains invariant as the chirp is manipulated. These properties are fundamentally different than in the well-known Fourier-transform pulse shaper.     

Three-dimensional spatiotemporal pulse characterization with an acousto-optic pulse shaper and a Hartmann-Shack wavefront sensor

We demonstrate a simplified arrangement for spatiotemporal ultrashort pulse characterization called Hartmann-Shack assisted, multidimensional, shaper-based technique for electric-field reconstruction. It employs an acousto-optic pulse shaper in combination with a second-order nonlinear crystal and a Hartmann-Shack wavefront sensor. The shaper is used as a tunable bandpass filter, and the wavefronts and intensities of quasimonochromatic spectral slices of the pulse are obtained using the Hartmann-Shack wavefront sensor. The wavefronts and intensities of the spectral slices are related to one another using shaper-assisted frequency-resolved optical gating measurements, performed at particular points in the beam. This enables a three-dimensional reconstruction of the amplitude and phase of the pulse. We present some example pulse measurements and discuss the operating parameters of the device.     

Dispersion-free fiber transmission for femtosecond pulses by use of a dispersion-compensating fiber and a programmable pulse shaper

We demonstrate nearly distortionless 2.5-km fiber transmission of sub-500-fs pulses, using a combination of standard single-mode fiber, dispersion-compensating fiber, and a programmable pulse shaper for simultaneous quadratic and cubic dispersion compensation. The dispersion-compensating fiber corrects the bulk of the quadratic and the cubic phases for the single-mode fiber, and the fiber-pigtailed programmable pulse shaper exactly compensates the residual dispersion terms. Together these elements permit complete recompression of pulses, which first broaden by ~400 times in the single-mode fiber.     

Fully dispersion-compensated approximately 500 fs pulse transmission over 50 km single-mode fiber

We demonstrate essentially distortionless 50 km fiber transmission for approximately 500 fs pulses, using dispersion-compensating fiber and a programmable pulse shaper as a spectral phase equalizer. This distance is approximately five times longer than previously achieved at similar pulse widths.     

Grism-based pulse shaper for line-by-line control of more than 600 optical frequency comb lines

We construct a line-by-line pulse shaper using a grism (grating plus prism) dispersive element, which provides constant angular dispersion over 13.4 THz centered at ~311 THz (965 nm). When combined with a dual-mask liquid crystal modulator, this grism-based shaper is capable of line-by-line amplitude and phase control of over 600 modes of a 21 GHz stabilized optical frequency comb.     

Tomographic retrieval of the polarization state of an ultrafast laser pulse

We introduce a self-referenced method for determining the complete polarization state of an ultrafast pulse field. The algorithm is based on any well-established technique that measures both the intensity and phase of a single polarization, such as frequency-resolved optical gating (FROG). We demonstrate the retrieval of nontrivial fields generated using a polarization-amplitude-phase ultrafast pulse shaper using four standard FROG measurements.     

Bright and dark 40 GHz parabolic pulse generation using a picosecond optical pulse train and an arrayed waveguide grating

We demonstrate parabolic optical pulse generation by manipulating the intensity and phase of individual longitudinal modes of a 40 GHz picosecond optical pulse train in the spectral domain. Bright and dark parabolic pulses were generated from a 40 GHz mode-locked fiber laser using a 64-channel arrayed waveguide grating pulse shaper. The obtained parabolic pulse, which can easily generate a linear chirping, is useful for a number of applications to optical signal processing applications, including pulse compression and time-domain optical Fourier transformation.     

Real-time edge enhancement of femtosecond time-domain images by use of photorefractive quantum wells

Dynamic holograms written in a photorefractive multiple quantum well placed inside a Fourier femtosecond pulse shaper convert a space-domain image into the time domain. We demonstrate that edge-enhancement processing of the time-domain image can be performed by controlling hologram-writing intensities.     

Generation of polarization-shaped ultraviolet femtosecond pulses

We experimentally demonstrate the generation and characterization of polarization-shaped femtosecond laser pulses in the ultraviolet at a central wavelength of 400 nm. Near-infrared laser pulses are first polarization shaped and then frequency doubled in an interferometrically stable setup that employs two perpendicularly oriented nonlinear crystals. A new pulse shaper design involving volume phase holographic gratings reduces losses and hence leads to an increase in pulse energy.     

入射波整形技术的实验和理论研究

 在硅橡胶材料的分离式霍普金森压杆实验中,实验研究了如何实现常应变率加载,并且得到了整形器尺寸与加载应变率之间,以及加载应变率与试样厚度之间的定量关系。根据预估入射波形的理论模型,给出了采用H62黄铜整形器整形后入射波形的计算结果和实验结果,二者基本上是一致的。     

Intense femtosecond pulse shaping using a fused-silica spatial light modulator

We present the design concept of a setup of a pulse shaper to be used for high-power femtosecond lasers. The pulse shaper is constructed from a high-damage threshold fused-silica spatial light modulator and a 4-f optical system based on the design concept to avoid optical damage. We have successfully demonstrated a pulse compression of 20 fs, 5 mJ pulses obtained from a 1 kHz repetition rate Ti:sapphire chirped pulse amplification system at an average power of 5 W.     

Femtosecond optical packet generation by a direct space-to-time pulse shaper

We demonstrate femtosecond operation of a direct space-to-time pulse shaper in which there is direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. We use this apparatus to generate trains of 20 pulses as an ultrafast optical data packet over an ~40-ps temporal window.     

Real-time one-dimensional coherent imaging through single-mode fibers by space time conversion processors

We introduce and experimentally demonstrate a novel technique for one-dimensional coherent imaging through a single-mode optical fiber by use of a pulse shaper and a pulse imager. In contrast to the wavelength-division-multiplexed encoding technique, our approach preserves both amplitude and phase information of the optical signal transmitted through the fiber, allowing one to encode longitudinal in addition to transverse optical information. The effect of the fiber-material dispersion on our imaging technique is analyzed, and potential solutions are discussed.     

Femtosecond-pulse sequence compression by Gires-Tournois interferometers

We demonstrate the compression of femtosecond-pulse sequences by phase-modulating resonators, such as Gires-Tournois interferometers. The experiments are based on the precompensation of the complex phase response of the resonator by a high-resolution liquid-crystal pulse shaper. This method can be utilized for lowering peak intensities at critical points in optical setups, as well as for encryption or decryption of ultra-short pulses.     

Femtosecond direct space-to-time pulse shaping in an integrated-optic configuration

We demonstrate femtosecond operation of an integrated-optic direct space-to-time pulse shaper for which there is a direct mapping (no Fourier transform) between the spatial position of the masking function and the temporal position in the output waveform. The apparatus is used to generate trains of more than 30 pulses as an ultrafast optical data packet over approximately an 80-ps temporal window.