Accepted papers to appear in an upcoming issue
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Nearly lattice Matched MoS2/GaN Heterostructure Enabling High Performance Phototransistors
Xinke Liu, yuxuan chen, Dabing Li, Sheng-Wen Wang, chao-cheng ting, Lin Chen, Kah-Wee Ang, Chengwei Qiu, Yu-Lun Chueh, Sun Xiaojuan, and Hao-chung Kuo
Doc ID: 357440 Received 11 Jan 2019; Accepted 17 Jan 2019; Posted 17 Jan 2019 View: PDF
Abstract: MoS2-based phototransistor is attractive for optical electronics in a large-scale size, such as transparent touch screen etc. However, most of the work done over the past decade is on opaque SiO2/Si wafer with a small size (μm-mm). In this work, large-scale multilayer MoS2-based phototransistor has been fabricated on transparent free-standing (FS) GaN wafer using a scalable chemical vapor deposition method. Due to the nearly lattice match and small thermal expansion mismatch between GaN and MoS2, the as-grown multilayer MoS2-on-GaN film shows high material quality in term of low full width at half maximum (FWHM~5.16 cm-1) for Raman mode, and high absorption coefficient α (~106 cm-1) in the wavelength range of 405-638 nm. Under a wavelength of 405 nm at incident power of 2 mW and applied voltage of 9 V, the fabricated MoS2-on-GaN phototransistor achieved a maximum responsivity of 17.2 A/W, photocurrent gain of 53.6, and external quantum efficiency (EQE) of 5289%, with specific detectivity (~1010-1012 Jones) and low noise equivalent power (10-12~10-14 W/Hz1/2) in the visible range of 405-638 nm. A typical response time of 0.1-4s in the air ambient has also been recorded for the demonstrated MoS2-on-GaN phototransistor. Our work paves a technologic stepping stone for MoS2-based phototransistors for multifunctional transparent and touch-based optoelectronics in the future.
In situ instant photo-generating and multiple modulating ultra-broadband bismuth near infrared emission inside borosilicate glasses via ultrafast femtosecond laser
Liping Wang, jiangkun cao, Yao Lu, XiaoMan Li, Shanhui Xu, Qinyuan Zhang, Zhongmin Yang, and Mingying Peng
Doc ID: 342665 Received 20 Aug 2018; Accepted 12 Jan 2019; Posted 15 Jan 2019 View: PDF
Abstract: Optical amplification are extremely crucial to the realization of integrated planar photonic circuits because they can compensate signal degradation and speed up the performance of integrated components. Significant efforts have been made to implement waveguide amplification in the host glasses and silicon substrate. Unfortunately, no studies have been realized that the amplification bandwidth could cover the whole optical telecommunication window. Bismuth (Bi) doped photonic materials, has been investigated substantially relying on broadband near infrared (NIR) luminescence. However, Bi-based NIR luminescence metamaterials are scarcely fabricated successfully owing to the sensitivity of Bi NIR active ions to the complex microstructure. Here, we showed that Bi NIR emission from 1000 to 1600 nm can be in situ generated instantly in the grating region by femtosecond (fs) laser inside borosilicate glasses. A series of structural and spectroscopic characterizations were employed to explore the generation mechanism. Furthermore, we managed to enhance the NIR emission of grating region by photo-ionization effect. We also showed how these emission can be erased flexibly through appropriate thermal stimulation. Finally, ultra-broadband NIR emission from Bi-doped optical waveguides was demonstrated successfully inside glasses. These results present new insights into Bi-doped materials and contribute to the development of waveguide amplification.
Efficient spectrum prediction and inverse design for plasmonic waveguide systems based on artificial neural networks
tian zhang, Jia Wang, Qi Liu, Jinzan Zhou, Jian Dai, Xu Han, Yue Zhou, and Kun Xu
Doc ID: 351485 Received 09 Nov 2018; Accepted 11 Jan 2019; Posted 15 Jan 2019 View: PDF
Abstract: In this article, we propose a novel approach to achieve spectrum prediction, parameter fitting, inverse design and performance optimization for the plasmonic waveguide coupled with cavities structure (PWCCS) based on artificial neural networks (ANNs). The Fano resonance and plasmon induced transparency effect originated from the PWCCS have been selected as illustrations to verify the effectiveness of ANNs. We use the genetic algorithm to design the network architecture and select the hyper-parameters for ANNs. Once ANNs are trained by using a small sampling of the data generated by Monte Carlo method, the transmission spectrums predicted by the ANNs are quite approximate to the simulated results. The physical mechanisms behind the phenomena are discussed theoretically, and the uncertain parameters in the theoretical models are fitted by utilizing the trained ANNs. More importantly, our results demonstrate that this model-driven method not only realizes the inverse design of the PWCCS with high precision but also optimizes some critical performance metrics for transmission spectrum. Compared with previous works, we construct a novel model-driven analysis method for the PWCCS which are expected to have significant applications in the device design, performance optimization, variability analysis, defect detection, theoretical modeling, optical interconnects and so on.
Demonstration of an on-chip TE-pass polarizer using silicon hybrid plasmonic grating
Bowen Bai, Fenghe Yang, and Zhiping Zhou
Doc ID: 352662 Received 23 Nov 2018; Accepted 11 Jan 2019; Posted 15 Jan 2019 View: PDF
Abstract: An on-chip, high extinction ratio transverse electric pass polarizer using silicon hybrid plasmonic grating is proposed and experimentally demonstrated on silicon-on-insulator platform. Utilizing the optical confinement of plasmonics, transverse magnetic mode is reflected and absorbed while transverse electric mode passes through with relatively low propagation loss. For a 6 μm-long device, the measurement result shows that the extinction ratio in the wavelength range of 1.52 μm to 1.58 μm varies from 24 dB to 33.7 dB and the insertion loss is 2.8–4.9 dB. Moreover, the structure exhibits large fabrication tolerance and compatible with silicon-on-insulator fabrication technology.
Ternary ReS2(1-x)Se2x alloy saturable absorber for passively Q-switched and Mode-locked Erbium-doped all-fiber lasers
Dou Chenxi, wen wen, Junli Wang, mengyuan ma, L. M. Xie, Ching-Hwa Ho, and Zhiyi Wei
Doc ID: 346142 Received 17 Sep 2018; Accepted 08 Jan 2019; Posted 09 Jan 2019 View: PDF
Abstract: We report Q-switched and mode-locked Erbium-doped all-fiber lasers using ternary ReS2(1-x)Se2x as saturable absorbers (SAs). The modulation depth and saturable intensity of the film SA are 1.8 % and 0.046 MW/cm2. In Q-switched pulse output was centered at 1531.1 nm with maximum pulse energy and minimum pulse width of 28.29 nJ and 1.07 µs, respectively. In mode-locked operation, the pulse was centered at 1561.15 nm with pulse width of 888 fs, repetition rate of 2.95 MHz, and the maximum pulse energy of 0.275 nJ. To the best of our knowledge, this is the first report on the mode-locked Er-doped fiber laser using ternary transition metal dichalcogenides (TMDs).This work suggests a prospective two dimensional(2D) material SAs, which can be widely used in versatility fields due to its attractive optoelectronic and its tunable energy bandgap properties.
Subwavelength negative-index waveguiding enabled by coupled spoof magnetic localized surface plasmons
Zhen Liao, Bengeng Cai, baicao pan, Guoqing Luo, and wenhui cao
Doc ID: 347115 Received 01 Oct 2018; Accepted 03 Jan 2019; Posted 04 Jan 2019 View: PDF
Abstract: Magnetic localized surface plamsons modes are supported on metallic spiral structures. Coupling mechanisms for this metamaterial resonators are studied, which are the joint action of magnetic and electric coupling. Based on the strong coupling, localized surface magnetic modes propagating with backward direction are proposed along a chain of subwavelength resonators. The numerical simulations and experiments are in good agreements. The proposed novel route for achieving negative-index waveguiding has potential applications in integrated devices and circuits.1. Introduction
Silica nano cone array as a template for fabricating plasmon induced hot electron photodetector
Zhiqiang Yang, Kang Du, Fanfan Lu, Yang Pang, Shijia Hua, Xuetao Gan, Wending Zhang, Ting Mei, and Soo Jin Chua
Doc ID: 348617 Received 19 Oct 2018; Accepted 03 Jan 2019; Posted 04 Jan 2019 View: PDF
Abstract: Plasmon induced hot electrons have attracted a great deal of interest as a novel route for photodetection and light-energy harvesting. Herein, we report a hot electron photodetector in which a large array of nanocones with Al, TiO2 and Au films deposited on it can be integrated with nanophotonics and microelectronics. The device exhibits a strong photo-electric response at around 620 nm, with a responsivity of 180 μA/W under short-circuit conditions with a significant increase under 1V reverse bias to 360 μA/W. The increased in responsivity and red shift in peak value with increasing bias voltage indicate that the bias causes an increase in the hot electron tunneling effect. Our approach will be advantageous for the implementation of the proposed architecture on a vast variety of integrated optoelectronic devices.
Low-noise InGaAs/InP single-photon detector with widely-tunable operation frequency
Yan Liang, Heping Zeng, Qilai Fei, and Zhihe Liu
Doc ID: 348714 Received 18 Oct 2018; Accepted 30 Dec 2018; Posted 02 Jan 2019 View: PDF
Abstract: InGaAs/InP avalanche photodiodes (APDs) typically work in the gated Geiger mode to achieve near-infrared single-photon detection. By using ultrashort gates and combining with the robust spike-cancelling technique that consists of the capacitance-balancing and low-pass filtering technique, we demonstrate an InGaAs/InP single-photon detector (SPD) with widely-tunable operation frequency in this paper. The operation frequency could be tuned conveniently from 100 MHz to 1.25 GHz with the SPD’s performance measured to keep well, making it quite suitable for quantum key distribution, laser ranging and optical time domain reflectometry. Furthermore, the SPD exhibited extremely low-noise characteristics. The detection efficiency of this SPD could reach 20% with the dark count rate of 2.5×10-6/gate and afterpulse probability of 4.1% at 1 GHz.
Photonics-based radar with balanced I/Q de-chirping for interference-suppressed high-resolution detection and imaging
Shilong Pan, Xingwei Ye, Fangzheng Zhang, and Yue Yang
Doc ID: 346958 Received 28 Sep 2018; Accepted 24 Dec 2018; Posted 02 Jan 2019 View: PDF
Abstract: Photonics-based radar with photonic de-chirp receiving has advantages of broadband operation and real-time signal processing, but it suffers from interferences of the image-frequencies and other undesired frequency mixing components, due to the single channel real-valued photonic frequency mixing. In this paper, we propose a photonics-based radar with a photonic frequency-doubling transmitter and a balanced I/Q de-chirp receiver. This radar transmits broadband linearly frequency-modulated signals generated by photonic frequency-doubling, and performs I/Q de-chirping of the radar echoes based on a balanced photonic I/Q frequency mixer, which is realized by applying a 90° optical hybrid followed by balanced photodetectors. The proposed radar has a high range resolution because of the large operation bandwidth, and achieves interference-free detection by suppressing the image-frequencies and other undesired frequency mixing components. In the experiment, a photonics-based K band radar with a bandwidth of 8 GHz is demonstrated. The balanced I/Q de-chirping receiver achieves an image-rejection ratio over 30 dB, and successfully eliminates the interference due to the baseband envelope and the frequency mixing between radar echoes of different targets. Besides, the desired de-chirped signal power is also enhanced with balanced detection. Based on the established photonics-based radar, inverse synthetic aperture radar imaging is also implemented, through which, advantages of the proposed radar is verified.
Highly stable femtosecond pulse generation from a MXene mode-locked fiber laser
Chujun Zhao, Jie Li, zilong zhang, Lin Du, Lili Miao, jun yi, Bin Huang, Yanhong Zou, and Shuangchun Wen
Doc ID: 349316 Received 31 Oct 2018; Accepted 23 Dec 2018; Posted 02 Jan 2019 View: PDF
Abstract: Ultrafast fiber lasers are in great demand for various applications, such as optical communication, spectroscopy, biomedical diagnosis, and industrial fabrication. Here, we report the highly stable femtosecond pulse generation from a MXene mode-locked fiber laser. We have prepared the high quality Ti₃C₂Tx nanosheets via etching method, and characterized their ultrafast dynamics and the broadband nonlinear optical responses. The obvious intensity- and wavelength-dependent nonlinear responses have been observed and investigated. In addition, a highly stable femtosecond fiber laser with SNR up to 70.7 dB and central wavelength of 1567.3 nm has been delivered. The study may provide some valuable design guidelines for the development of ultrafast, broadband nonlinear optical modulators, and open new avenues toward advanced photonic devices based on MXenes.
Enlarge the bandwidth of slow light in fishbone like grating waveguides
Ran Hao, GaoYang Ye, Jianyao Jiao, and Erping Li
Doc ID: 345437 Received 13 Sep 2018; Accepted 23 Dec 2018; Posted 02 Jan 2019 View: PDF
Abstract: Slow light, a technology to control the optical signal by reducing the group velocity, has been widely studied to obtain enhanced nonlinearities and increased phase shifts owing to its promoting light-matter interaction ability. In this work, a wide band slow light is achieved in a simple one-dimensional fishbone waveguide. A flat band indicating slow light with group index of 13 and bandwidth over 10nm is obtained by plane wave expansion calculation and measured through the experiment. Meanwhile, by introducing a grating coupler, the coupling efficiency could be improved remarkably from below 20% to 60%.
Ultrabroadband wavelength-swept source based on total mode-locking of a Yb:CaF₂ laser
Maciej Kowalczyk, Tadeusz Martynkien, Pawel Mergo, Grzegorz Sobon, and Jaroslaw Sotor
Doc ID: 342584 Received 17 Aug 2018; Accepted 18 Dec 2018; Posted 18 Dec 2018 View: PDF
Abstract: We present an ultrabroadband, high speed wavelength-swept source based on a self-modulated femtosecond oscillator. Photonic crystal fiber was pumped by a mode-locked Yb:CaF₂ laser resulting in a strong spectral broadening from 485 to 1800 nm. The pump laser cavity could be realigned in order to achieve total mode-locking of the longitudinal and transverse TEM₀₀ and TEM₀₁ electromagnetic modes. This led to spatial oscillations of the output beam, which induced modulation of the coupling efficiency to the fiber. Due to the fact that nonlinear spectral broadening was intensity-dependent, this mechanism introduced wavelength sweeping at the fiber output. The sweeping rate could be adjusted between 7 and 21.5 MHz by changing the geometry of the pump cavity. By controlling the ratio of the transverse mode amplitudes we were able to tune the sweeping bandwidth, eventually covering both 1300 nm and 1700 nm bioimagining transparency windows. When compared with previously demonstrated wavelength-swept sources, our concept offers much broader tunability and higher speed. Moreover, it does not require any additional intensity modulator.
Hot-wire CVD low-loss a-Si:H waveguides for silicon photonic devices
Swe Oo, Antulio Tarazona, Ali Khokhar, Rafidah Petra, Yohann Franz, Goran Mashanovich, Graham Reed, Anna Peacock, and Harold Chong
Doc ID: 331501 Received 11 May 2018; Accepted 18 Dec 2018; Posted 21 Dec 2018 View: PDF
Abstract: We demonstrate low-loss hydrogenated amorphous silicon (a-Si:H) waveguides by hot-wire chemical vapor deposition (HWCVD). The effect of hydrogenation in a-Si at different deposition temperatures has been investigated and analyzed by Raman spectroscopy. We obtained optical quality a-Si:H waveguide deposited at 0 ºC that has a strong Raman peak shift at 480 cm-1, peak width, FWHM of 68.9 cm-1 and bond angle deviation of 8.98 º. Optical transmission measurement shows a low propagation loss of 0.65 dB/cm at 1550 nm wavelength, which is the first reported for HWCVD a-Si:H waveguide.
Generation of coexisting high energy pulses in a mode-locked all-fiber laser with nonlinear multimodal interference technique
GuangWei Chen, li lei, Guomei Wang, Wenfu Zhang, Chao Zeng, and Wei Zhao
Doc ID: 349553 Received 30 Oct 2018; Accepted 17 Dec 2018; Posted 17 Dec 2018 View: PDF
Abstract: We demonstrate a passively mode-locked all-fiber laser incorporating a piece of graded-index multimode fiber as a mode-locking modulator based on nonlinear multimodal interference technique, which generates two types of coexisting high energy ultrashort pulses, i.e. the conventional soliton (CS) and stretched pulse (SP). The CS with pulse energy as high as 0.38 nJ is obtained at the pump level of 130 mW. When the pump increases to 175 mW, the high energy SP occurs at suitable nonlinear phase bias and its pulse energy can reach 4 nJ at 610 mW pump. The pulse durations of the generated CS and SP are 2.3 ps and 387 fs, respectively. The successive single-shot spectra of them, measured by dispersive Fourier-transform technique, show significantly diverse buildup dynamics of CS and SP mode-locking from previous reports. The simulation results, based on generalized nonlinear Schrödinger equation, reveal that these two types of high energy pulses coexist in the passively mode-locked fiber laser, which agrees well with the experimental observations. The proposed all-fiber laser is versatile, easy integration, and cost-effective, which provides a promising solution for high energy pulse generations.
Conversion between polarization states based on metasurface
Shuyun Teng, Qi Zhang, Han Wang, Lixia Liu, and HaoRan Lü
Doc ID: 346340 Received 20 Sep 2018; Accepted 12 Dec 2018; Posted 13 Dec 2018 View: PDF
Abstract: Transmission of anisotropic metasurface is analyzed in polar base relying on the Jones calculus and the polarization conversion from the spatial uniform polarization to the spatial non-uniform polarization is explored. The simple and compact polarization converters based on the rectangular holes etched in the silver film are designed, and the polarization conversions from the linear and circular polarization to the radial and azimuthal polarization are realized. Numerical simulations about three designed polarization converters consisting of the rectangular holes respectively equivalent to polarizers, quarter and half wave plates exhibit the perfect polarization conversion. The experiment results consistent with the simulations verify theoretic predictions. This study is helpful for designing metasurface polarization converters and expanding the applications of metasurface in polarization manipulations.
Enhanced Four-Wave Mixing Process Near the Excitonic Resonances of Bulk MoS₂
Brian Ko, Alexei Sokolov, Marlan Scully, Zhang Rong, and Ho Wai Lee
Doc ID: 349643 Received 31 Oct 2018; Accepted 11 Dec 2018; Posted 11 Dec 2018 View: PDF
Abstract: Two-dimensional materials are generating great interest due to their unique electrical and optical properties. In particular, transitional metal dichalcogenides such as MoS₂ are an attractive material due to the existence of a direct band gap in the monolayer limit that can be used to enhance nonlinear optical phenomena, such as Raman spectroscopy. Here, we have investigated four-wave mixing processes in bulk MoS₂ using a multiplex coherent anti-Stokes Raman spectroscopy setup. The observed four-wave mixing signal has a resonance at approximately 680 nm, corresponding to the energy of the A excitonic transition of MoS₂. This resonance can be attributed to the increased third-order nonlinear susceptibility at wavelengths near the excitonic transition. This phenomenon could open the path to using MoS₂ as a substrate for enhancing four-wave mixing processes such as coherent anti-Stokes Raman spectroscopy.
Wideband adaptive microwave frequency identification using an integrated silicon photonic scanning filter
Xu Wang, Feng Zhou, Dingshan Gao, Yanxian Wei, Xi Xiao, Shaohua Yu, Jianji Dong, and Xinliang Zhang
Doc ID: 345236 Received 06 Sep 2018; Accepted 09 Dec 2018; Posted 11 Dec 2018 View: PDF
Abstract: Photonic-assisted microwave frequency identification with distinct features including wide frequency coverage and fast tunability, has been conceived as a key technique for applications such as cognitive radio and dynamic spectrum access. The implementations based on the compact integrated photonic chips have exhibited intriguing advantages in footprint miniaturization, light weight and low power consumption, in stark contrast to the discrete optical-fiber-based realization. However, the reported chip-based instantaneous frequency measurements can only operate at a single-tone input, which stringently limits their practical deployment that require wideband identification capability in modern RF and microwave applications. In this article, we demonstrate, for the first time, a wideband, adaptive microwave frequency identification solution based on a silicon photonic integrated chip, enabling the identification of different types of microwave signals from 1 to 30 GHz, including single-frequency, multiple-frequency, chirped-frequency, frequency-hopping microwave signals, and even their combinations. The key component is a high-Q-factor scanning filter based on a silicon microring resonator, which is used to implement frequency-to-time mapping. This demonstration opens the door to a monolithic silicon platform that enable the wideband, adaptive and high speed signal identification subsystem with a high resolution and a low SWaP for mobile and avionic applications.
Effective suppression of stimulated Raman scattering in half 10 kilowatt tandem pumping fiber lasers using chirped and tilted fiber Bragg gratings
Meng Wang, Zefeng Wang, Le Liu, Qihao Hu, Hu Xiao, and Xiaojun Xu
Doc ID: 347322 Received 02 Oct 2018; Accepted 08 Dec 2018; Posted 11 Dec 2018 View: PDF
Abstract: The average power of fiber lasers have been scaled deep into the kW regime in the past years. However, stimulated Raman scattering (SRS) is a major factor limiting the further power scaling. Here, we have demonstrated for the first time, to the best of our knowledge, the suppression of SRS in a half 10 kilowatt tandem pumping fiber amplifier using chirped and tilted fiber Bragg gratings (CTFBGs). With specially self-designed and manufactured CTFBGs inserted between the seed laser and the amplifier stage, a maximum SRS suppression ratio of >15 dB in spectrum is observed with no reduce in laser efficiency. With one CTFBG, the effective output power is improved to 3.9 kW with beam quality M2 factor of ~1.7 from <3.5 kW with M2 factor of >2; with two CTFBGs, the effective laser power reaches to 4.2 kW with an increasing ratio of 20% and M2 factor of ~1.8, and further power promotion is limited by the power and performance of the 1018 nm pump sources. This work provides an effective SRS suppression method for high-power all-fiber lasers, which is very useful for the further power scaling of these systems.
Coupling Strategies for Silicon Photonics Integrated Chips
Cosimo Lacava, Riccardo Marchetti, Lee Carroll, Kamil Gradkowski, and Paolo Minzioni
Doc ID: 338163 Received 06 Jul 2018; Accepted 06 Dec 2018; Posted 13 Dec 2018 View: PDF
Abstract: In the last 20 years, silicon photonics has revolutionized the field of integrated optics, providing a novel and powerful platform to build mass-producible optical circuits. One of the most attractive peculiarity of silicon photonics is its ability to supply extremely small optical components, whose typical dimensions are order of magnitude smaller than optical fiber devices. This dimension discrepancy makes the design of fiber-to chip interfaces extremely challenging and, over the years, has stimulated an incredibly large amount of research efforts in the field. Fiber-to-Silicon photonic chip interfaces can be broadly divided into two big categories: in-plane and out-of-plane couplers. Devices falling in the first category typically offer high coupling efficiency, large coupling bandwidth (in wavelength) and no polarization dependence, but they require relatively complex fabrication procedures and do not allow for wafer-scale testing.Conversely, out-of-plane device offer lower efficiency, limited bandwidth and are typically polarization dependent. However they are compatible with high-volume fabrication processes, and allow on-wafer accessing any part of the optical circuit. In this paper we review the current state of the art of optical couplers, aiming to give to the reader a comprehensive and broad view of the field, identifying advantages and disadvantages of each solution proposed.As fiber-to-chip couplers are inherently related to packaging technologies, and the co-design of optical packages has become essential, we also review in this document the main solutions currently used to package and assemble optical fibers with Silicon-photonic integrated circuits.
High-power and high-energy laser generation at 1834 nm in a Nd:YAG single-crystal fiber laser oscillator
Bin Xu, yaqi cai, Yunshan Zhang, qingyu tian, Xiaodong Xu, Qingsong Song, Dongzhen Li, Jun Xu, and Ivan Buchvarov
Doc ID: 351312 Received 08 Nov 2018; Accepted 06 Dec 2018; Posted 07 Dec 2018 View: PDF
Abstract: We report on diode-end-pumped high-power and high-energy Nd:YAG single-crystal fiber laser at 1834 nm. Two 808-nm diodes injecting about 58-W pump power into the Nd:YAG fiber have generated 3.28-W continuous-wave and 1.66-W Cr:ZnSe-based passively Q-switched lasers. Slope efficiencies with respect to pump powers are 8.7% for the continuous-wave laser and 4.9% for the Q-switched laser. The extracted maximum pulse energy is about 266.9 μJ and the corresponding maximum pulse peak power is 2.54 kW. These performances greatly surpass previous results regarding this specific laser emission because laser gain medium in the form of fiber can significantly mitigate thermally induced power saturation thanks to its significantly reduced thermal lensing effect. Single-crystal fiber lasers show great potential for high average power, pulse energy and peak power.