Frequency-resolved Optical Gating Measurements Research Articles

Observation of Ultrashort Laser Pulse Evolution in a Silicon Photonic Crystal Waveguide

Using the sum frequency generation cross-correlation frequency-resolved optical gating (SFG-XFROG) measurement setup, we observed the soliton evolution of low energy pulse in an Si photonic crystal waveguide, and it exhibited the pulse broadening, blue shift, and evident pulse acceleration. The soliton evolution was also investigated by nonlinear Schrödinger equation (NLSE) modelling simulation, and the simulated results agreed well with the experimental measurements. The effects of waveguide length on the pulse evolution were analyzed; the results showed that the pulse width changed periodically with increasing waveguide length. The results further the understanding of the ultra-fast nonlinear dynamics of solitons in silicon waveguides, and are helpful to soliton-based functional elements on CMOS-compatible platforms.

Temperature and Pulse-Energy Range Suitable for Femtosecond Pulse Transmission in Si Nanowire Waveguide

We experimentally measured the femtosecond pulse transmission through a silicon-on-insulator (SOI) nanowire waveguide under different temperatures and input pulse energy with a cross-correlation frequency-resolved optical gating (XFROG) measurement setup. The experimental results demonstrated that the temperature and pulse energy dependence of the Si photonic nanowire waveguide (SPNW) is interesting rather than just monotonous or linear, and that the suitable temperature and pulse-energy range is as suggested in this experiment, which will be valuable for analyzing the practical design of the operating regimes and the fine dispersion engineering of various ultrafast photonic applications based on the SPNWs. The research results will contribute to developing the SPNWs with photonic elements and networks compatible with mature complementary metal–oxide–semiconductors (CMOS).

Generation of Intense Sub-10 fs Pulses at 385nm* *Supported by the National Key Research and Development Program of China (Grant No. 2019YFA0307703), the Major Research Plan of NSF of China (Grant No. 91850201), and the National Natural Science Foundation of China (Grant Nos. 11974426, 11974425, U1830206 and 11604386).

We demonstrated the generation and characterization of 9.7 fs, 180 μJ pulses centered at 385 nm via the frequency doubling of few-cycle near-infrared pulses. Both moderate conversion efficiency (9.5%) and broad phase matching bandwidth (20 nm) were achieved by shaping the spectra of the fundamental pulses. The strong intensity dependence of second-order harmonic generation and well controlled material dispersion ensured the inexistence of satellite pulses, which was confirmed by the self-diffraction frequency resolved optical gating measurement.

Self-Referencing Spectral Interferometric Probing of the Onset Time of Relativistic Transparency in Intense Laser-Foil Interactions

Irradiation of an ultrathin foil target by a high intensity laser pulse drives collective electron motion and the generation of strong electrostatic fields, resulting in ultrabright sources of high-order harmonics and energetic ions. The ion energies can be significantly enhanced if the foil undergoes relativistic self-induced transparency during the interaction, with the degree of enhancement depending in part on the onset time of transparency. We report on a simple and effective approach to diagnose the time during the interaction at which the foil becomes transparent to the laser light, providing a route to optically controlling and optimizing ion acceleration and radiation generation. The scheme involves a self-referencing approach to spectral interferometry, in which coherent transition radiation produced at the foil rear interferes with laser light transmitted through the foil. The relative timing of the onset of transmission with respect to the transition radiation generation is determined from spectral fringe spacing and compared to simultaneous frequency-resolved optical gating measurements. The results are in excellent agreement, and are discussed with reference to particle-in-cell simulations of the interaction physics and an analytical model for the onset time of transparency in ultrathin foils.

Temporal characterization of femtosecond laser pulses using tunneling ionization in the UV, visible, and mid-IR ranges

To generalize the applicability of the temporal characterization technique called “tunneling ionization with a perturbation for the time-domain observation of an electric field” (TIPTOE), the technique is examined in the multicycle regime over a broad wavelength range, from the UV to the IR range. The technique is rigorously analyzed first by solving the time-dependent Schrödinger equation. Then, experimental verification is demonstrated over an almost 5-octave wavelength range at 266, 1800, 4000 and 8000 nm by utilizing the same nonlinear medium – air. The experimentally obtained dispersion values of the materials used for the dispersion control show very good agreement with the ones calculated using the material dispersion data and the pulse duration results obtained for 1800 and 4000 nm agree well with the frequency-resolved optical gating measurements. The universality of TIPTOE arises from its phase-matching-free nature and its unprecedented broadband operation range.

Measurement for optical arbitrary waveforms using cross-phase modulation cross-correlation frequency-resolved optical gating in a single-mode fibre

A novel scheme of cross-correlation frequency-resolved optical gating (X-FROG) measurement for optical arbitrary waveforms based on the photo-elastic effect and cross-phase modulation (XPM) effect in a single-mode fibre is proposed. In this scheme, a variable delay is generated in the former part of the single-mode fibre by a uniform lateral pressure, and the XPM effect is achieved in the latter part of the fibre. The proposed scheme is very simple and easy to be realized. The amplitude and phase of optical arbitrary waveform to be measured is retrieved from the X-FROG trace using principal component generalized projects algorithm based on matrix. The impacts of the shape of gate pulse, fibre length, relative intensity between gate pulse and optical arbitrary waveform and the complexity of the optical arbitrary waveform on the accuracy of retrieved amplitude and phase are investigated. Simulation results show that, rectangular pulse is a better gate pulse due to lower errors. The accuracy of measurement is improved with the increase in fibre length, and relative intensity between gate pulse and optical arbitrary waveform. Moreover, this scheme also can be used to measure extremely complex optical arbitrary waveforms.

Cross-correlation frequency-resolved optical gating scheme based on a periodically poled lithium niobate waveguide for an optical arbitrary waveform measurement

This study proposes a novel scheme of a crosscorrelation frequency-resolved optical gating (X-FROG) measurement for an optical arbitrary waveform (OAW) based on the sum frequency generation (SFG) effect of a periodically poled lithium niobate (PPLN) waveguide. Based on the SFG effect and combined with the principal component generalized projects algorithm on a matrix, the theory model of the scheme is established. Using Matlab, the proposed OAW measurement X-FROG scheme using the PPLN waveguide is simulated and studied. Simulation results show that a rectangular pulse is a suitable gate pulse because of its low errors. Moreover, the increased complexity of OAW and phase mismatch decrease measurement accuracy.

Group Delay measurements of ultrabroadband pulses generated in highly nonlinear fibers

Ultra broadband supercontinuum pulses are commonly used as a source of different wavelengths from a wide spectral bandwidth or as a source of very short pulses. However the processes responsible for wide spectral broadening are still under investigation. In this paper we examine the temporal and spectral characteristics of the pulses broadened upon propagation in the highly nonlinear photonics crystal fibers with different dispersion profiles. Generated supercontinuum pulses were experimentally characterized using cross-correlation frequency resolved optical gating technique. Full Text: PDF ReferencesM. Bradler, P. Baum, and E. Riedle, "Femtosecond continuum generation in bulk laser host materials with sub-?J pump pulses", Appl. Phys. B 97, 561 (2009). CrossRef T. M. Kardas, B. Ratajska-Gadomska, W. Gadomski, A. Lapini, and R. Righini, "The role of stimulated Raman scattering in supercontinuum generation in bulk diamond", Opt. Express 21, 24201 (2013). CrossRef A. Brodeur and S. L. Chin, "Band-Gap Dependence of the Ultrafast White-Light Continuum", Phys. Rev. Lett. 80, 4406 (1998). CrossRef R. R. Alfano, ed., The Supercontinuum Laser Source: Fundamentals with Updated References, 2nd ed (Springer, 2006). DirectLink A. L. Gaeta, Phys. "Catastrophic Collapse of Ultrashort Pulses", Rev. Lett. 84, 3582 (2000). CrossRef J. M. Dudley, G. Genty, and S. Coen, "Supercontinuum generation in photonic crystal fiber", Rev. Mod. Phys. 78, 1135 (2006). CrossRef M. Klimczak, B. Siwicki, P. Skibinski, D. Pysz, R. Stepien, A. Heidt, C. Radzewicz, and R. Buczynski, "Coherent supercontinuum generation up to 2.3 ?m in all-solid soft-glass photonic crystal fibers with flat all-normal dispersion", Opt. Express 22, 18824 (2014). CrossRef D. J. Kane and R. Trebino, "Characterization of arbitrary femtosecond pulses using frequency-resolved optical gating", IEEE J. Quantum Electron. 29, 571 (1993). CrossRef J. Dudley, X. Gu, L. Xu, M. Kimmel, E. Zeek, P. O'Shea, R. Trebino, S. Coen, and R. Windeler, "Cross-correlation frequency resolved optical gating analysis of broadband continuum generation in photonic crystal fiber: simulations and experiments", Opt. Express 10, 1215 (2002). CrossRef N. Nishizawa and T. Goto, "Experimental analysis of ultrashort pulse propagation in optical fibers around zero-dispersion region using cross-correlation frequency resolved optical gating", Opt. Express 8, 328 (2001). CrossRef X. Gu, L. Xu, M. Kimmel, E. Zeek, P. O'Shea, A. P. Shreenath, R. Trebino, and R. S. Windeler, "Frequency-resolved optical gating and single-shot spectral measurements reveal fine structure in microstructure-fiber continuum", Opt. Lett. 27, 1174 (2002). CrossRef S. Roy, S. K. Bhadra, and G. P. Agrawal, "Effects of higher-order dispersion on resonant dispersive waves emitted by solitons", Opt. Lett. 34, 2072?2074 (2009). CrossRef S. Bose, S. Roy, R. Chattopadhyay, M. Pal, and S. K. Bhadra, "Experimental and theoretical study of red-shifted solitonic resonant radiation in photonic crystal fibers and generation of radiation seeded Raman soliton", J. Opt. 17, 105506 (2015). CrossRef T. Roger, M. F. Saleh, S. Roy, F. Biancalana, C. Li, and D. Faccio, "High-energy, shock-front-assisted resonant radiation in the normal dispersion regime", Phys. Rev. A 88, (2013). CrossRef G. P. Agrawal, Nonlinear Fiber Optics, Fifth edition (Elsevier/Academic Press, 2013). DirectLink J. Szczepanek, T. Kardas, M. Nejbauer, C. Radzewicz, and Y. Stepanenko, "Simple all-PM-fiber laser system seeded by an all-normal-dispersion oscillator mode-locked with a nonlinear optical loop mirror", Proc. SPIE 9728, 972827 (2016). CrossRef C. Iaconis and I. A. Walmsley, "Self-referencing spectral interferometry for measuring ultrashort optical pulses", IEEE J. Quantum Electron. 35, 501 (1999). CrossRef L. E. Hooper, P. J. Mosley, A. C. Muir, W. J. Wadsworth, and J. C. Knight, "Coherent supercontinuum generation in photonic crystal fiber with all-normal group velocity dispersion", Opt. Express 19, 4902 (2011). CrossRef J. Szczepanek, T. M. Kardas, and Y. Stepanenko, "Sub-160-fs pulses dechriped to its Fourier transform limit generated from the all-normal dispersion fiber oscillator", Optical Society of America Frontiers in Optics conference, FTu3C?2 (2016). CrossRef G. Genty, M. Lehtonen, and H. Ludvigsen, "Effect of cross-phase modulation on supercontinuum generated in microstructured fibers with sub-30 fs pulses", Opt. Express 12, 4614 (2004). CrossRef S. Roy, S. K. Bhadra, K. Saitoh, M. Koshiba, and G. P. Agrawal, "Dynamics of Raman soliton during supercontinuum generation near the zero-dispersion wavelength of optical fibers", Opt. Express 19, 10443 (2011). CrossRef Y. Liu, Y. Zhao, J. Lyngso, S. You, W. L. Wilson, H. Tu, and S. A. Boppart, "Suppressing Short-Term Polarization Noise and Related Spectral Decoherence in All-Normal Dispersion Fiber Supercontinuum Generation", J. Light. Technol. 33, 1814 (2015). CrossRef

Improved retrieval of complex supercontinuum pulses from XFROG traces using a ptychographic algorithm.

We demonstrate that time-domain ptychography, a recently introduced iterative ultrafast pulse retrieval algorithm, has properties well suited for the reconstruction of complex light pulses with large time-bandwidth products from a cross-correlation frequency-resolved optical gating (XFROG) measurement. It achieves temporal resolution on the scale of a single optical cycle using long probe pulses and low sampling rates. In comparison to existing algorithms, ptychography minimizes the data to be recorded and processed, and significantly reduces the computational time of the reconstruction. Experimentally, we measure the temporal waveform of an octave-spanning, 3.5 ps long, supercontinuum pulse generated in photonic crystal fiber, resolving features as short as 5.7 fs with sub-fs resolution and 30 dB dynamic range using 100 fs probe pulses and similarly large delay steps.

Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire

The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication.

Direct measurement of time-frequency analogs of sub-Planck structures

Exploiting the correspondence between Wigner distribution function and a frequency-resolved optical gating (FROG) measurement, we experimentally demonstrate existence of the chessboard-like interference patterns with a time-bandwidth product smaller than that of a transform-limited pulse in the phase space representation of compass states. Using superpositions of four electric pulses as realization of compass states, we have shown via direct measurements that displacements leading to orthogonal states can be smaller than limits set by uncertainty relations. In the experiment we observe an exactly chronocyclic correspondence to the sub-Planck structure in the interference pattern appearing for superposition of two Sch\"{o}dinger-cat-like states in a position-momentum phase space.

Pulse reshaping in nearly resonant interaction of femtosecond pulses with dense rubidium vapor

Propagation of intense femtosecond pulses resonant with the atomic rubidium vapor results in phenomenon known as conical emission. The origin of this phenomenon is connected with self-phase modulation in time domain accompanied with spatial self-focusing for blue-detuned pulses. When the laser central wavelength is red-detuned the self-defocusing occurs. Using frequency-resolved optical gating measurements and simple modeling of pulse propagation within the linear dispersion theory it is shown that the retrieved phase of the propagated pulse, and the associated instantaneous frequency, shows evidence of both linear dispersion and self-phase modulation. These results are consistent with the theory of the intensity dependent nonlinear refraction index in medium where linear dispersion contributes significantly to pulse reshaping.

Autocorrelation and Frequency-Resolved Optical Gating Measurements Based on the Third Harmonic Generation in a Gaseous Medium

A gas was utilized in producing the third harmonic emission as a nonlinear optical medium for autocorrelation and frequency-resolved optical gating measurements to evaluate the pulse width and chirp of a Ti:sapphire laser. Due to a wide frequency domain available for a gas, this approach has potential for use in measuring the pulse width in the optical (ultraviolet/visible) region beyond one octave and thus for measuring an optical pulse width less than 1 fs.

Stable and high-power few cycle supercontinuum for 2D ultrabroadband electronic spectroscopy.

Broadband supercontinuum (SC) pulses in the few cycle regime are a promising source for spectroscopic and imaging applications. However, SC sources are plagued by poor stability, greatly limiting their utility in phase-resolved nonlinear experiments such as 2D photon echo spectroscopy (2D PES). Here, we generated SC by two-stage filamentation in argon and air starting from 100fs input pulses, which are sufficiently high-power and stable to record time-resolved 2D PE spectra in a single laser shot. We obtain a total power of 400μJ/pulse in the visible spectral range of 500-850nm and, after compression, yield pulses with duration of 6fs according to transient-grating frequency-resolved optical gating (TG-FROG) measurements. We demonstrate the method on the laser dye, Cresyl Violet, and observe coherent oscillations indicative of nuclear wavepacket dynamics.

Three-photon excitation source at 1250 nm generated in a dual zero dispersion wavelength nonlinear fiber.

We demonstrate 1250 nm pulses generated in dual-zero dispersion photonic crystal fiber capable of three-photon excitation fluorescence microscopy. The total power conversion efficiency from the 28 fs seed pulse centered at 1075 nm to pulses at 1250 nm, including coupling losses from the nonlinear fiber, is 35%, with up to 67% power conversion efficiency of the fiber coupled light. Frequency-resolved optical gating measurements characterize 1250 nm pulses at 0.6 nJ and 2 nJ, illustrating the change in nonlinear spectral phase accumulation with pulse energy even for nonlinear fiber lengths < 50 mm. The 0.6 nJ pulse has a 26 fs duration and is the shortest nonlinear fiber derived 1250 nm pulse yet reported (to the best of our knowledge). The short pulse durations and energies make these pulses a viable route to producing light at 1250 nm for multiphoton microscopy, which we we demonstrate here, via a three-photon excitation fluorescence microscope.

Supercontinuum pulse measurement by $$\hbox {KNbO}_{3}$$ KNbO 3 nanoneedle based cross-correlation frequency-resolved optical gating (XFROG)

In this paper, we investigate the sum-frequency properties of potassium niobate ( $$\hbox {KNbO}_{3}$$ ) nanoneedles. Based on the results, we achieve a rough Cross-correlation frequency-resolved optical gating (XFROG) measurement of super-continuum pulses, including the pulse’s‘ time/frequency-dependent intensity. This approach is promising in several aspects: First, due to the nanometer scale, the phase matching constraint can be naturally satisfied over the wide band of SC spectra, and the phase-matching apparatus can be eliminated. Meanwhile, the phase-matching modulation is more straightforward, which makes the measurement system more accessible for common users. Therefore, our $$\hbox {KNbO}_{3}$$ nanoneedles based XFROG approach provides a feasible choice for SC pulses estimation.

Femtosecond laser pulse compression using angle of incidence optimization of chirped mirrors

Optimal pulse compression following spectral broadening in a noble gas-filled hollow core fiber is a critical step towards producing isolated attosecond pulses. Here we present a systematic pulse shaping method based on the optimal selection of chirped mirrors and on the optimization of their angle of incidence. Feedback from second harmonic frequency resolved optical gating measurements is used to compute the optimal chirped mirror configuration of the next iteration in a genetic algorithm. Sub-5 fs pulses were achieved after a few iterations.

Cross-phase modulation typed frequency resolved optical gating measurement for ultra-short pulses using a single mode fiber

A new scheme of measuring ultra-short optical pulses, based on the photo-elastic effect and cross-phase modulation (XPM) effect in a single-mode fiber, is proposed. In this novel scheme, a variable delay is generated in the former part of the single-mode fiber, and the nonlinear effect is produced in the latter part as a nonlinear medium. The structure including only one single-mode fiber is very simple and low-cost, and needs no complex optical circuit calibration. In addition, XPM effect in the fiber can be realized easily without phase matching. Measured pulses can be retrieved by using principal component generalized projects algorithm based on matrix, and the influences of fiber length and the pulse width on amplitude and phase are studied by numerically simulating the scheme proposed. The results show that the ultra-short optical pulses can be measured when fiber length is equal to 2 km, and the accuracy of measurement is improved by increasing the fiber length. The proposed scheme can realize the measurement of optical ultra-short pulse whose pulse width is above 80 fs.

Up-conversion of a megahertz mid-IR supercontinuum

We present an cross-correlation frequency-resolved optical gating (XFROG) measurement of a megahertz IR supercontinuum generated in a step-index ZBLAN fiber. The resulting spectrogram gives the dispersion characteristics of the fiber and reveals that it has three zero-dispersion wavelengths. A comparison of the measured spectrogram with numerical simulations shows that this dispersion profile allows a notable dispersive-wave generation toward long wavelengths. Furthermore, the sum-frequency generation process in the XFROG measurement gives the possibility of measuring the IR light with fast Si-based detectors, such as CCD arrays.

Transform-limited pulses for chirped-pulse amplification systems utilizing an active feedback pulse shaping technique enabling five time increase in peak power

A fiber-based chirped-pulse amplification (CPA) system with an active feedback loop for pulse shaping is experimentally demonstrated. A spectral processor is used in conjunction with a frequency-resolved optical gating measurement to produce high-quality pulses. Spectral phase and intensity shaping are utilized to generate a clean, high-contrast, transform-limited pulse with 15 dB pedestal suppression in the pulse wing tails, resulting in a five time increase in peak power of the CPA system.