Self-referenced Spectral Interferometry Research Articles

Self-Referenced Spectral Interferometry for Single-Shot Characterization of Ultrashort Free-Electron Laser Pulses.

An attosecond x-ray pulse with known spectrotemporal information is an essential tool for the investigation of ultrafast electron dynamics in quantum systems. Ultrafast free-electron lasers (FELs) have the unique advantage on unprecedented high intensity at x-ray wavelengths. However, no suitable method has been established so far for the spectrotemporal characterization of these ultrashort x-ray pulses. In this Letter, a simple method has been proposed based on self-referenced spectral interferometry for reconstructing the temporal profile and phase of ultrashort FEL pulses. We have demonstrated that the proposed method is reliable to completely characterize the attosecond x-ray FEL pulses with an error at the level of a few percent. Moreover, the first proof-of-principle experiment has been performed to achieve the single-shot spectrotemporal characterization of ultrashort pulses from a high-gain FEL. The precision of the proposed method will be enhanced with the decrease of the pulse duration, paving a new way for complete attosecond pulse characterization at x-ray FELs.

Self-referencing similariton-based spectral interferometry for ultrashort pulse complete characterization

Similariton is used to provide a reference for the characterization of ultrashort pulses by spectral interferometry. Measured pulse profiles are compared with autocorrelation measurements and cross-checked by spectrotemporal imaging technique based on similariton-induced temporal lens. The use of similariton makes the pulse measurement method self-referencing, substantially improving its application range, whilst preserving the simplicity of the principle and setup of the classic methods of spectral interferometry that require a reference pulse. Our comparative experimental study, carried out together with numerical simulations, provides the application range and limitations of the method and evidences the high precision of the similariton-based spectral interferometry.

Dynamic range enhancement of self-referenced spectral interferometry with extended time excursion method by the cascaded Kerr lens process.

Self-referenced spectral interferometry with extended time excursion (SRSI-ETE) is a powerful method for single-shot characterization of the temporal contrast of a high peak power laser, which has high temporal resolution but a low dynamic range. Here, a temporal contrast reduction method is proposed that uses the cascaded Kerr lens process in two thin glass plates. Combined with the SRSI-ETE method, the measurement dynamic range of the method is increased about two orders of magnitude while having a 20fs temporal resolution and a 40ps time window in single shot.

The Temporal Measurement of Infrared Femtosecond Fiber Laser Pulse with Complex Spectra: SPIDER and FROG

Femtosecond fiber laser pulse (FFLP) is very suitable for precision laser processing (PLP) with the advantages of high power, compact integrated structure, and easy installation. However, with the power increasing, nonlinear optical effects (NOE) of fiber, such as self-phase modulation (SPM), will be greatly enhanced, and the spectra of the output pulse will be very complex, which considerably increases the temporal complexity of FFLP and takes an immeasurable influence on PLP, so it is of great significance to accurately measure the temporal property of FFLP for higher accuracy of PLP. This paper presents a self-referencing spectral phase interferometry for direct electric-field reconstruction based on a single grating stretcher (SGS-SPIDER) with the two-step phase shift (TSPS) method for measuring FFLP with complex and infrared spectra. Meanwhile, we present a modified pulse-retrieval algorithm called an adaptive pulse-retrieval algorithm (APRA) of frequency-resolved optical gating (FROG) to reconstruct the measured pulse accurately. The duration of the reconstructed pulse measured by FROG is 162 fs, whose autocorrelation curve is similar to the measured autocorrelation curve including the picosecond background. The error of the reconstructed FROG trace is 0.42%, which is reliable enough according to the literature experience. Finally, the unique advantages of FROG for measuring complex ultrashort pulses such as FFLP are compared with SPIDER; that is, FROG has a wider spectral phase measuring range than SPIDER. These studies provide a new diagnostic technique for the complete temporal characterization of FFLP with complex spectra and extend the measurement range and application of SPIDER at the infrared wavelength band, which is significant for improving the accuracy of PLP using FFLP.

Broad spectral range few-cycle laser pulses characterization by using a FASI device

Full characterization of few-cycle laser pulses is necessary in many applications. FROG is one of the most widely used full characterization techniques so far, and SRSI is another fresh one with attractive capacity. In this study, we develop a simple device FASI (frequency-resolved optical gating and self-referenced spectral interferometry), which combines the FROG and SRSI in a single device, and both of them are based on the third-order nonlinear effect of transient grating. It is compact with a size of 340 × 240 × 80 mm3. The device owns the advantages of the TG-SRSI method, which can characterize few-cycle pulses with broad spectral range from UV to mid-IR in single-shot mode for well compressed pulses. What’s more, for complex or large chirped pulses, it can also complete the characterization task by using the multi-shot TG-FROG mode. Two few-cycle pulses centered at 800 nm and 1800 nm have been characterized by using this device to verify its ability. It turned out that the proposed FASI device is a powerful tool for broad spectral range few-cycle laser pulses characterization.

Characterization of Accumulated B-Integral of Regenerative Amplifier Based CPA Systems

We report on a new approach to measure the accumulated B-integral in the regenerative and multipass amplifier stages of ultrashort-pulse high-power laser systems by B-integral-induced coupling between delayed test post-pulses and the main pulse. A numerical model for such non-linear pulse coupling is presented and compared to data taken at the high-power laser Draco with self-referenced spectral interferometry (SRSI). The dependence of the B-integral accumulated in the regenerative amplifier on its operation mode enables optimization strategies for extracted energy vs. collected B-integral. The technique presented here can, in principle, be applied to characterize any type of ultrashort pulse laser system and is essential for pre-pulse reduction.

Single-Shot Measurement of Post-Pulse-Generated Pre-Pulse in High-Power Laser Systems

In this study, a detailed investigation of the dynamics of the generation of pre-pulse by post-pulses is presented, using single-shot self-referenced spectral interferometry (SRSI). The capability of SRSI in terms of the single-shot measurement of the temporal contrast of high-power laser systems has been experimentally demonstrated. The results confirm that the energy levels of the pre-pulses increase proportional to the square of the B-integral parametrizing the nonlinearity of the amplifier chain.

All-reflective self-referenced spectral interferometry for single-shot measurement of few-cycle femtosecond pulses in a broadband spectral range

An all-reflective self-referenced spectral interferometry based on the transient grating (TG) effect is proposed for single-shot measuring of the amplitude and phase of ultrashort pulses in a broadband spectral range. Except for a thin third-order nonlinear medium, which was used to generate the TG signal, no transmitted optics were used in the proposed device, and few-cycle pulses in a broad spectral range from deep UV to mid-IR can be characterized. With a homemade compact and alignment-free device, a 5.0 fs pulse at 800 nm corresponding to about two cycles and a 14.3 fs pulse at 1800 nm corresponding to less than three cycles were successfully characterized.

Double-pulse characterization by self-referenced spectral interferometry

The reconstruction of ultrashort optical pulses with a complex intensity substructure is demonstrated using the Self-Referenced Spectral Interferometry (SRSI) pulse characterization technique with a modified phase retrieval algorithm. A correction spectral phase term is extracted by the manipulation of the temporal interferogram, allowing the treatment of scenarios with complicated pulse shapes, where the original algorithm fails. The improved SRSI algorithm is verified through the application on two temporally well-separated pulses having the same polarization direction and spectral shape, generated by duplicating 37 fs-long amplified pulses of a Ti:Sa based laser system. The spectral phase of highly chirped double pulses with equal or different amplitude ratios is numerically retrieved. The collinear and achromatic experimental arrangement results in a compact and easy-to-align system.

A compact and alignment-free tube-type device for femtosecond pulses measurement.

A compact and alignment-free device based on transient grating self-referenced spectral interferometry is proposed to realize the temporal profile measurement of femtosecond laser pulses. The entire optical setup is composed of two lenses and two glass plates on a straight line with tubes, thereby avoiding complicated optical alignment and improving the stability and practicality of the device. Two 51.0 fs and 16.9 fs laser pulses at 800 nm and a 60.6 fs pulse at 1800 nm are all successfully measured by this device, which verifies the reliability of the device.

On-shot characterization of single plasma mirror temporal contrast improvement

We report on the setup and commissioning of a compact recollimating single plasma mirror (PM) for temporal contrast enhancement at the Draco 150 TW laser during laser-proton acceleration experiments. The temporal contrast with and without PM is characterized single-shot by means of self-referenced spectral interferometry with extended time excursion at unprecedented dynamic and temporal range. This allows for the first single-shot measurement of the PM trigger point, which is interesting for the quantitative investigation of the complex pre-plasma formation process at the surface of the target used for proton acceleration. As a demonstration of high contrast laser plasma interaction we present proton acceleration results with ultra-thin liquid crystal targets of ∼ 1 μm down to 10 nm thickness. Focus scans of different target thicknesses show that highest proton energies are reached for the thinnest targets at best focus. This indicates that the contrast enhancement is effective such that the acceleration process is not limited by target pre-expansion induced by laser light preceding the main laser pulse.

High dynamic, high resolution and wide range single shot temporal pulse contrast measurement.

A novel apparatus for the single-shot measurement of the temporal pulse contrast of modern ultra-short pulse lasers is presented, based on a simple yet conceptual refinement of the self-referenced spectral interferometry (SRSI) approach. The introduction of the spatial equivalent of a temporal delay by tilted beams analyzed with a high quality imaging spectrometer, enables unprecedented performance in dynamic, temporal range and resolution simultaneously. Demonstrated consistently in simulation and experiment at the front-end of the PW laser Draco, the full range of the ps temporal contrast defining the quality of relativistic laser-solid interaction could be measured with almost 80 dB dynamic range, 18ps temporal window, and 18fs temporal resolution. Additionally, spatio-temporal coupling as in the case of a pulse front tilt can be quantitatively explored.

Self-Referenced Spectral Interferometry for Femtosecond Pulse Characterization

Since its introduction in 2010, self-referenced spectral interferometry (SRSI) has turned out to be an analytical, sensitive, accurate, and fast method for characterizing the temporal profile of femtosecond pulses. We review the underlying principle and the recent progress in the field of SRSI. We present our experimental work on this method, including the development of self-diffraction (SD) effect-based SRSI (SD-SRSI) and transient-grating (TG) effect-based SRSI (TG-SRSI). Three experiments based on TG-SRSI were performed: (1) We built a simple TG-SRSI device and used it to characterize a sub-10 fs pulse with a center wavelength of 1.8 μm. (2) On the basis of the TG effect, we successfully combined SRSI and frequency-resolved optical gating (FROG) into a single device. The device has a broad range of application, because it has the advantages of both SRSI and FROG methods. (3) Weak sub-nanojoule pulses from an oscillator were successfully characterized using the TG-SRSI device, the optical setup of which is smaller than the palm of a hand, making it convenient for use in many applications, including sensor monitoring the pulse profile of laser systems. In addition, the SRSI method was extended for single-shot characterization of the temporal contrast of ultraintense and ultrashort laser pulses.

Compact transient-grating self-referenced spectral interferometry for sub-nanojoule femtosecond pulse characterization.

The self-referenced spectral interferometry (SRSI) technique, which is usually used for microjoule-level femtosecond pulse characterization, is improved to characterize weak femtosecond pulses with nanojoule based on the transient-grating effect. Both femtosecond pulses from an amplifier with 3 nJ per pulse at 1 kHz repetition rates and femtosecond pulses from an oscillator with less than 0.5 nJ per pulse at 84 MHz repetition rates are successfully characterized. Furthermore, through a special design, the optical setup of the device is even smaller than a palm, which will make it simple and convenient during the application. These improvements extend the application of the SRSI technique to the characterization of femtosecond pulses in a broad range. Not only pulses from an amplifier but also pulses from an oscillator or weak pulses used in ultrafast spectroscopy can be monitored with this SRSI method right now.

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

Compact design for two-dimensional electronic spectroscopy

We present a passively phase-stabilized two-dimensional electronic spectroscopy (2DES) with a compact size, and the ease of implementation and maintenance. Our design relies on a mask beam-splitter with four holes to form non-collinear box geometry, and a homebuilt stacked retroreflector, which introduces the phase-locked pulse sequence, remedying the instability of commonly used translation stages. The minimized size of the setup suppresses the influences of optical path-length fluctuations during measurements, improving the phase stability and precise timing of pulse sequences. In our 2DES, only few conventional optical components are used, which make this sophisticated instrumentation convenient to establish and particularly easy to conduct alignment. In data analysis, the self-referencing spectral interferometry (SRSI) method is first introduced to extract the complex-valued signal from spectral interferometry in 2DES. The alternative algorithm achieves the improvement of the signal-to-noise ratio (SNR) and considerable reduction of data acquisition time. The new setup is suitable over a tunable range of spectroscopic wavelength, from ultraviolet (UV) to the near-infrared (NIR) regime, and for ultra-broadband bandwidth, few-cycle laser pulses.

Self-referenced spectral interferometry for single-shot measurement of sub-5-fs pulses.

We demonstrate a novel approach for the extension of self-referenced spectral interferometry to the temporal characterization of few-optical cycle pulses. The new experimental setup is characterized by low dispersion and a collinear geometry. 4-fs pulses have been characterized by performing single-shot measurements, with high dynamic range on a broad temporal region. An independent measurement of the pulse duration, obtained by using attosecond streaking, allowed us to cross-check the experimental technique.

Extended transient-grating self-referenced spectral interferometry for sub-100 nJ femtosecond pulse characterization

A geometry of transient-grating self-referenced spectral interferometry (TG-SRSI) is proposed for weak femtosecond pulse characterization. By using a reflective microscope objective (RMO), we build a compact, robust, and easy to adjust device with a higher sensitivity to pulse energy in comparison to all previous SRSI methods. A 65 nJ/∼40 fs/1 kHz pulse at 800 nm is successfully characterized, which speaks to the capability of our device to characterize a weak pulse. It is expected to extend the TG-SRSI method to the characterization of femtosecond pulses from oscillators in the near future.

Measurement of energy contrast of amplified ultrashort pulses using cross-polarized wave generation and spectral interferometry.

We present a method using spectral interferometry (SI) to characterize a pulse in the presence of an incoherent background such as amplified spontaneous emission (ASE). The output of a regenerative amplifier is interfered with a copy of the pulse that has been converted using third-order cross-polarized wave generation (XPW). The ASE shows as a pedestal background in the interference pattern. The energy contrast between the short-pulse component and the ASE is retrieved. The spectra of the interacting beams are obtained through an improvement to the self-referenced spectral interferometry (SRSI) analysis.

Standards for ultrashort-laser-pulse-measurement techniques and their consideration for self-referenced spectral interferometry.

Issues important for new ultrashort-pulse-measurement techniques include the generation of theoretical example traces for common pulses, validity ranges, ambiguities, coherent artifacts, device calibration sensitivity, iterative retrieval convergence, and feedback regarding measurement accuracy. Unfortunately, in the past, such issues have gone unconsidered, yielding long histories of unsatisfactory measurements. We review these issues here in the hope that future proposers of new techniques will consider them without delay, and, as an example, we address them for a relatively new technique: self-referenced spectral interferometry.