We demonstrate an extremely simple frequency-resolved-optical-gating (GRENOUILLE) device for measuring the
intensity and phase of relatively long-ps-pulses. In order to achieve the required high spectral resolution and large
temporal range, it uses a few-cm-thick second-harmonic-generation crystal in the shape of a pentagon. This has the
additional advantage of reducing the device's total number of components to as few as three simple easily aligned optics,
making it the simplest device ever developed for complete pulse measurement. We report complete intensity-and-phase
measurements of pulses up to 15ps long with a time-bandwidth product of 21.
Frequency-Resolved Optical Gating (FROG) and its variations are the only techniques available for measuring complex
pulses without a well-characterized reference pulse. We study the performance of the FROG generalized-projections
(GP) algorithm for retrieving the intensity and phase of very complex ultrashort laser pulses in the presence of noise.
Also, we show that a highly simplified version of FROG, GRENOUILLE, can easily measure visible pulses. By tuning a
thick crystal, it can cover the entire visible spectrum, which is typically generated from commercial Optical Parameter
We describe two novel, practical ultrashort laser pulse measurement devices, which are also experimentally very simple. The first one is an "ultra-broadband" pulse characterization device that is based on FROG, but uses transient grating (TG) process. TG FROG involves forming an induced grating in a piece of glass by crossing two pulses in space and time and then diffracting a third pulse off it to create a fourth <i>diffracted</i> pulse. The TG process is inherently very broadband and automatically phasematched. We have implemented an ultrasimple TG FROG device, which can also operate single-shot. First, three beams are created using a simple mask. Then, a cylindrical beams line-focuses the beams horizontally, where the induced grating is generated. The variation of the relative delay is achieved by crossing the two grating-creation beams at an angle using a Fresnel biprism. Then, by detecting the diffracted pulse with spatial resolution, the TG FROG trace is captured. The second device that we present aims to measure ultrashort pulses with complex spectral and temporal structure. <i>Spectral interferometry</i> (SI) works perfectly for this purpose. SI simply involves measuring the spectrum of the sum of the unknown (shaped) and known (reference) light waves. Unfortunately, SI is very difficult to align and maintain aligned, as it requires that the two beams be <i>nearly perfectly collinear</i>. We solved this problem by utilizing optical fibers. Spectral resolution is also significantly improved by using spatial fringes, avoiding time-domain filtering.