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Showing papers in "IEEE Journal of Quantum Electronics in 1992"


Journal ArticleDOI
TL;DR: The theory of quasi-phase-matched second-harmonic generation in both the space domain and the wave vector mismatch domain is presented in this paper, where various types of errors in the periodicity of these structures are analyzed to find their effects on the conversion efficiency and on the shape of the tuning curve.
Abstract: The theory of quasi-phase-matched second-harmonic generation is presented in both the space domain and the wave vector mismatch domain. Departures from ideal quasi-phase matching in periodicity, wavelength, angle of propagation, and temperature are examined to determine the tuning properties and acceptance bandwidths for second-harmonic generation in periodic structures. Numerical examples are tabulated for periodically poled lithium niobate. Various types of errors in the periodicity of these structures are then analyzed to find their effects on the conversion efficiency and on the shape of the tuning curve. This analysis is useful for establishing fabrication tolerances for practical quasi-phase-matched devices. A method of designing structures having desired phase-matching tuning curve shapes is also described. The method makes use of varying domain lengths to establish a varying effective nonlinear coefficient along the interaction length. >

2,137 citations


Journal ArticleDOI
TL;DR: In this paper, the absorption and emission cross sections of the transition between the ground spin-orbit multiplet and the lowest excited multiplet were measured for Er/sup 3+/, Tm/sup3+/, and Ho/Sup 3+/ ions in a variety of crystalline hosts.
Abstract: The absorption and emission cross sections of the transition between the ground spin-orbit multiplet and the lowest excited multiplet were measured for Er/sup 3+/, Tm/sup 3+/, and Ho/sup 3+/ ions in a variety of crystalline hosts. The materials that were investigated include LiYF/sub 4/, BaY/sub 2/F/sub 8/, Y/sub 3/Al/sub 5/O/sub 12/, LaF/sub 3/, KCaF/sub 3/, YAlO/sub 3/, and La/sub 2/Be/sub 2/O/sub 5/. The absolute magnitudes of the emission cross sections were determined from the absorption spectra, with the aid of the principle of reciprocity. The calculated radiative emission lifetimes derived from these measured cross sections agree well with the measured emission decay times for most materials. The potential use of these rare-earth-doped materials in pulsed laser applications requires that the ground state exhibit adequate splitting to minimize the detrimental effects of the ground state thermal population, and also that the emission cross section be sufficiently large to permit efficient extraction energy. The systems based on Ho/sup 3+/ in the eightfold coordinated sites of LiYF/sub 4/, BaY/sub 2/F/sub 8/, and Y/sub 3/Al/sub 5/O/sub 12/ appear to be the most promising. >

839 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a detailed theoretical and experimental investigation of the nonlinear dynamics of a semiconductor laser with optical feedback, showing that the coherence collapsed state is a chaotic attractor and that chaos is reached for increasing feedback level through a quasi-periodic route interrupted by frequency locking.
Abstract: The authors present a detailed theoretical and experimental investigation of the nonlinear dynamics of a semiconductor laser with optical feedback. The results show that the coherence collapsed state is a chaotic attractor and that chaos is reached for increasing feedback level through a quasi-periodic route interrupted by frequency locking. Furthermore, the coexistence of two attractors, associated with the same external cavity mode, but having different relaxation oscillation frequencies, is demonstrated and explained. >

523 citations


Journal ArticleDOI
TL;DR: In this paper, a 128-element liquid crystal modulator is used to manipulate the phases of optical frequency components which are spatially dispersed within a grating-and-lens pulse shaping apparatus.
Abstract: Programmable shaping of femtosecond pulses by using a 128-element liquid crystal modulator to manipulate the phases of optical frequency components which are spatially dispersed within a grating-and-lens pulse shaping apparatus is described. This apparatus makes possible gray-level control of the spectral phases and allows modification of the pulse shape on a millisecond time scale under electronic control. Refinements in the design of the multielement modulator result in pulse shaping fidelity comparable to that which can be achieved with microlithographically fabricated masks. Several examples of pulse shaping operation, including pulse position modulation, programmable pulse compression, and adjustable cubic phase distortion, are described. >

485 citations


Journal ArticleDOI
TL;DR: In this article, the authors developed a model and derived analytical expressions for the modulation response, resonance frequency, damping rate, and K factor to include carrier transport effects on the high-speed properties of quantum-well lasers.
Abstract: Carrier transport can significantly affect the high-speed properties of quantum-well lasers. The authors have developed a model and derived analytical expressions for the modulation response, resonance frequency, damping rate, and K factor to include these effects. They show theoretically and experimentally that carrier transport can lead to significant low-frequency parasitic-like rolloff that reduces the modulation response by as much as a factor of six in quantum-well lasers. They also show that, in addition, it leads to a reduction in the effective differential gain and thus the resonance frequency, while the nonlinear gain compression factor remains largely unaffected by it. The authors present the temperature dependence data for the K factor as further evidence for the effects of carrier transport. >

449 citations


Journal ArticleDOI
TL;DR: In this paper, the IEEE/ANSI Std. 176, with a small but much needed modification for crystal class mm2, is recommended for reporting nonlinear interaction characteristics, and other frames are proposed which result in simpler rules than heretofore given for categorizing phase-matching loci, and for characterizing eigenmode polarizations, double refraction, effective nonlinear coupling, and first and second-order acceptance bandwidths (angular, spectral, thermal) along these loci.
Abstract: Standards which eliminate ambiguity in reporting nonlinear phenomena, especially in the increasingly complex realm of biaxial crystals, are proposed. In order to restore uniformity to the designation of crystallographic axes and crystal tensor properties, adoption of IEEE/ANSI Std. 176, with a small but much needed modification for crystal class mm2, is recommended. For the reporting of nonlinear interaction characteristics, other frames are proposed which result in simpler rules than heretofore given for categorizing phase-matching loci, and for characterizing eigenmode polarizations, double refraction, effective nonlinear coupling, and first- and second-order acceptance bandwidths (angular, spectral, thermal) along these loci. Similarities as well as differences between biaxial and uniaxial crystals are emphasized. >

422 citations


Journal ArticleDOI
TL;DR: In this article, a new boundary condition was proposed for beam propagation calculations that passes outgoing radiation freely with minimum reflection coefficient (as low as 3*10/sup -8/).
Abstract: A new boundary condition is presented for use in beam propagation calculations that passes outgoing radiation freely with minimum reflection coefficient (as low as 3*10/sup -8/). In conjunction with a standard Crank-Nicholson finite difference scheme, the assumption that the radiation field behaves as a complex exponential near the boundary is shown to result in a specific transparent boundary condition algorithm. In contrast to the commonly used absorber method, this algorithm contains no adjustable parameters, and is thus problem independent. It is shown to be accurate and robust for both two- and three-dimensional problems. >

392 citations


Journal ArticleDOI
TL;DR: In this article, a variety of As-based III-V crystalline semiconductor layers grown by molecular beam epitaxy over a range of very low substrate temperatures were experimentally observed.
Abstract: Ultrashort carrier lifetimes were experimentally observed in a variety of As-based III-V crystalline semiconductor layers grown by molecular beam epitaxy over a range of very low substrate temperatures. Time-resolved optical absorption, reflection, and photoconductive switching measurements with femtosecond resolution have been used to directly measure the ultrafast carrier dynamics in these materials. GaAs and In/sub 0.52/Al/sub 0.48/As grown at temperatures of 200 and 150 degrees C, respectively, exhibited subpicosecond carrier lifetimes, while lattice-mismatched In/sub x/Ga/sub 1-x/As on GaAs displayed a 7-ps carrier lifetime in material grown at 200 degrees C. A distinct decrease in carrier lifetime with decreasing growth temperature is documented for all three material systems. For epilayers annealed at high-temperature, resistivities are high, and thus these materials were found to be ideally suited for a number of ultrafast optoelectronic applications. A number of applications are reviewed and discussed. >

357 citations


Journal ArticleDOI
TL;DR: In this paper, analytic theories of additive pulse mode (APM) locking and Kerr lens mode (KLM) locking are developed and a comparison of the two methods are provided.
Abstract: Analytic theories of additive pulse mode (APM) locking and Kerr lens mode (KLM) locking are developed. They provide a means for comparison of the two methods. In single-cavity configurations, KLM locking and APM locking produce comparable ratios of amplitude to phase modulation. This ratio may be enhanced in KLM at the expense of cavity stability. APM can be used in all-fiber systems. >

335 citations


Journal ArticleDOI
TL;DR: In this article, a mode-locked semiconductor laser which incorporates multiple contacting segments is found to give improved performance over single-segment designs, where the functions of gain, saturable absorption, gain modulation, gain frequency, repetition rate tuning, wavelength tuning and electrical pulse generation can be integrated on a single semiconductor chip.
Abstract: Mode-locked semiconductor lasers which incorporate multiple contacting segments are found to give improved performance over single-segment designs. The functions of gain, saturable absorption, gain modulation, repetition rate tuning, wavelength tuning, and electrical pulse generation can be integrated on a single semiconductor chip. The optimization of the performance of mode-locked lasers in terms of material parameters, waveguiding parameters, electrical parasitics, and segment length is discussed experimentally and theoretically. >

304 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the operation of high-reflectivity quarter-wave (QW) dielectric mirrors at the bandstop center (Bragg) frequency, relevant for the design of small-cavity optoelectronic structures.
Abstract: The authors analyze the operation of high-reflectivity quarter-wave (QW) dielectric mirrors at the band-stop center (Bragg) frequency, relevant for the design of small-cavity optoelectronic structures. The energy penetration depth concept is used to determine a first-order linear approximation for the reduction of the mirror peak reflectivity of the QE mirror as a function of the mirror material parameters and the number of layers. The expression can be applied in the limit of small loss. The mathematical analysis and expressions for the absorptance and the peak reflectivity of a dielectric mirror with weak material absorption are presented. The use of the results is illustrated for a typical vertical cavity surface-emitting laser structure. >

Journal ArticleDOI
TL;DR: In this paper, the authors derived the relevant optical distortion profiles and maximum stresses as a function of length-to-diameter ratio and pump spot size in end-pumped solid-state laser rods.
Abstract: Thermal effects lead to upper limits on the maximum achievable power in end-pumped solid-state laser rods. Thermal fracture is an ultimate limitation on pump power, while optical distortions and depolarization leading to increased losses in the laser resonator tend to yield a lower upper bound on the pump power. The relevant optical distortion profiles and maximum stresses are derived as a function of length-to-diameter ratio and pump spot size. Length-to-diameter ratios up to 1.5 are considered. Edge-cooled and face-cooled active-mirror geometries are analyzed and compared directly. The problem is cast into a nondimensional form so that the results are applicable to arbitrary rod materials. >

Journal ArticleDOI
TL;DR: In this article, the scaling limits of diode-end-pumped Nd:YAG laser are analyzed by pumping geometry, thermal distortion, birefringence, and fracture.
Abstract: The authors analyze the scaling limits of diode-end-pumped Nd:YAG lasers imposed by pumping geometry, thermal distortion, birefringence, and fracture. A scalable 15-W output power diode-end-pumped laser which achieves a 60% slope efficiency is demonstrated. Thermal distortion in this laser is reduced from 2.6 waves to less than 0.15 waves with an aspheric laser rod. Depolarization is reduced by 40 times to less than 0.2% per pass using optical rotators. Modeling results, which accurately predict thermal distortion and birefringence, imply a thermal fracture-limited output power for short end-pumped rods less than 45 W. A dual rod design for an 80-W device is described. One of the four modules in this device has been assembled and tested, producing a CW output of 22.5 W. >

Journal ArticleDOI
TL;DR: In this paper, the requirements for stable ultrashort pulse generation in these novel femtosecond sources are addressed and theoretical considerations are backed up by experimental results obtained with a number of different laser systems.
Abstract: The emergence of new ultrafast optical modulation techniques has opened the way towards a new femtosecond laser technology based on solid-state gain media. The authors address the requirements for stable ultrashort pulse generation in these novel femtosecond sources. The theoretical considerations are backed up by experimental results obtained with a number of different laser systems. The conclusions drawn from the presented theoretical and experimental investigations provide general guidelines for the design and optimization of a wide range of femtosecond solid-state laser oscillators. >

Journal ArticleDOI
TL;DR: In this article, the saturation properties of ultrafast pulsed electromagnetic radiation generated by large-aperture photoconducting antennas as a function of optical excitation fluence were investigated.
Abstract: The authors describe the saturation properties of ultrafast pulsed electromagnetic radiation generated by large-aperture photoconducting antennas as a function of optical excitation fluence. A theory that predicts this effect is presented. The amplitude saturation of the radiation has been observed form antennas incorporating GaAs, InP, and radiation damaged silicon-on-sapphire consistent with theoretical expectations. The radiated fields were measured directly with a time resolution of 0.6 ps with the use of a large-aperture antennas as a detector. From these experimental studies, information about the high-speed response (i.e., the transient carrier mobility in the first few picoseconds after optical excitation) of the photoconductors incorporated in the antenna can be obtained under conditions of high applied electric fields and optical fluences. >

Journal ArticleDOI
TL;DR: In this article, a high-speed metal-semiconductor-metal photodetectors (MSM PDs) with finger spacing and width as small as 25 nm were fabricated on bulk and low-temperature (LT) grown GaAs and crystalline Si using ultra-high-resolution electron-beam lithography.
Abstract: Metal-semiconductor-metal photodetectors (MSM PDs) with finger spacing and width as small as 25 nm were fabricated on bulk and low-temperature (LT) grown GaAs and crystalline Si using ultra-high-resolution electron-beam lithography. High-speed electrooptic characterization with a 100-fs pulsed laser showed that the fastest MSM PDs had finger spacing and width, full width at half maximum response time, and 3-dB bandwidth, respectively, of 300 nm, 0.87 ps, and 0.51 THz for LT-GaAs; 100 nm, 1.5 ps, and 0.3 THz for bulk GaAs; and 100 nm, 10.7 ps, and 41 GHz for crystalline Si. Monte Carlo simulation was used to understand the impulse response of the MSM PDs and to explore the ultimate speed limitation of transmit-time-limited MSM PDs on GaAs and Si. Factors that are important to detector capacitance were identified using a conformal mapping method. Based on the experimental data, Monte Carlo simulation, and calculation of detector capacitance, scaling rules for achieving high-speed MSM PDs are presented. >

Journal ArticleDOI
C. Li1, C. Wyon, R. Moncorge
TL;DR: In this article, the results of an analysis of the optical properties of Er/sup 3+/ and (Er/sup 2/SiO/sub 5/ ) single crystals that have been grown by the Czokralski method are presented.
Abstract: The results of an analysis of the optical properties of Er/sup 3+/ and (Er/sup 3+/, Yb/sup 3+/) doped Y/sub 2/SiO/sub 5/ single crystals that have been grown by the Czokralski method are presented. These crystals emit a very interesting fluorescence in the eye-safe spectral range around 1550 nm and they can be pumped efficiently with laser diodes at around 980 nm. It is argued that comparable laser properties to that of the well-known phosphate glasses can be obtained. >

Journal ArticleDOI
Young-Kai Chen1, Ming C. Wu1
TL;DR: In this article, the authors present the principles of and recent progress in monolithic CPM quantum-well lasers and review their application in the field of quantum well-laser systems.
Abstract: Integration of the whole mode-locked laser onto a single piece of semiconductor offers a number of advantages, including total elimination of optical alignment processes, improved mechanical stability, and the generation of short optical pulses at much higher repetition frequencies. Semiconductor laser processing technologies were used to implement the colliding-pulse mode-locking (CPM) scheme, which is known to effectively shorten the pulses and increase stability, on a miniature monolithic semiconductor cavity. The principles of and recent progress in monolithic CPM quantum-well lasers are reviewed. >

Journal ArticleDOI
TL;DR: In this paper, several ultrafast optical pulse generation techniques utilizing external cavity semiconductor lasers are described, including active mode locking, passive mode lock, hybrid mode locking and several chirp compensation techniques.
Abstract: Several ultrafast optical pulse generation techniques utilizing external cavity semiconductor lasers are described. These techniques include active mode locking, passive mode locking, hybrid mode locking, and several chirp compensation techniques. Utilizing these techniques, optical pulses of 200 fs in duration with over 160 W of peak power have been generated, making these pulses both the shortest and most intense ever generated with a semiconductor injection diode laser system. These pulses have been used to study the ultrafast amplification characteristics of semiconductor lasers. The results presented reveal the nature of the effects which dominate the pulse shaping mechanisms in external cavity hybrid mode-locked diode lasers. >

Journal ArticleDOI
TL;DR: In this article, a theory was developed for fiber four-wave mixing where the polarization states of input light are various and they change randomly when propagating through a fiber line, and the results show that intensity beating between the propagating lights plays an important role in four-warp mixing efficiency in a fiber.
Abstract: Four-wave mixing in a single-mode fiber is studied for general polarization states in input lights. A theory is developed for fiber four-wave mixing where the polarization states of input light are various and they change randomly when propagating through a fiber line. The results show that intensity beating between the propagating lights plays an important role in four-wave mixing efficiency in a fiber. Experimental results support the theoretical treatment. >

Journal ArticleDOI
TL;DR: In this paper, a two-diode laser-pumped Nd:YAG laser has been frequency stabilized to a commercial 6.327 GHz free spectral range Fabry-Perot interferometer yielding a best-case beatnote linewidth of 330 mHz.
Abstract: Two-diode laser-pumped Nd:YAG lasers have been frequency stabilized to a commercial 6.327-GHz free spectral range Fabry-Perot interferometer yielding a best-case beatnote linewidth of 330 mHz. In addition, a Fabry-Perot interferometer with a free spectral range of 680 MHz, a linewidth of 25 kHz, and a finesse of 27500 has been built, and when substituted in place of the commercial interferometer produced a robust and easily repeatable beatnote linewidth of 700 MHz. >

Journal ArticleDOI
TL;DR: In this article, a terahertz time-domain spectrometer based on photoconductive dipole antennas driven by femtosecond laser pulses was used to measure the absorption and index of refraction for benzene, carbon tetrachloride, and cyclohexane in the far infrared.
Abstract: A newly developed terahertz time-domain spectrometer based on photoconductive dipole antennas driven by femtosecond laser pulses was used to measure the absorption and index of refraction for benzene, carbon tetrachloride, and cyclohexane in the far infrared. The spectra cover the region of 3-66 cm/sup -1/, where the dielectric response of the nonpolar liquids is dominated by collision induced dipole moments. With terahertz time-domain spectroscopy, information on both the real and imaginary part of the frequency response is obtained in a range difficult to access by standard techniques. >

Journal ArticleDOI
TL;DR: In this paper, a side-illuminated p-i-n photodetector with a multimode waveguide structure is proposed, which has an external quantum efficiency of 56% without AR coating and 68% with AR coating.
Abstract: A side-illuminated p-i-n photodetector with a multimode waveguide structure is proposed. Numerical and experimental results show that higher-order mode lights greatly enhance the coupling efficiency between the waveguide photodetector (WGPD) and a fiber, which leads to a high external quantum efficiency. The multimode WGPD has the major advantage that the external quantum efficiency and bandwidth can be derived independently of each other because the multimode waveguide structure can be designed without deteriorating electrical properties. The fabricated WGPD has an external quantum efficiency of 56% without AR coating and 68% with AR coating, and an electrical frequency 3 dB greater than 50 GHz at a 1.55- mu m wavelength. >

Journal ArticleDOI
TL;DR: In this article, the generation of coherent phonons by absorption of femtosecond laser pulses through interband transitions in different materials is summarized, starting with layered III-VI semiconductors, where optical excitation is performed with amplified pulses.
Abstract: The generation of coherent phonons by absorption of femtosecond laser pulses through interband transitions in different materials is summarized. Starting with layered III-VI semiconductors, where optical excitation is performed with amplified pulses, the generation mechanism via strong interband transitions is investigated. In Ge, stimulated resonant Raman scattering is found to be the decisive driving force. In GaAs, however, the ultrafast screening of surface space charge fields launches LO-phonons via electrostatic coupling. In the metallic state of high-temperature superconductors, the generation of highly symmetric A/sub g/ modes is assigned to displacive processes induced by a nonequilibrium electronic carrier distribution. In the superconducting state the amount of coherent displacement is strictly correlated to the number of optically broken superconducting pairs. In addition to the comparison of various generation processes, the dephasing of coherent phonons is addressed. >

Journal ArticleDOI
TL;DR: In this article, an all-solid-state passively mode-locked neodymium glass fiber laser is investigated by employing characterization techniques in the time, optical, and radio-frequency domains.
Abstract: Pulse formation in an all-solid-state passively mode-locked neodymium glass fiber laser is investigated by employing characterization techniques in the time, optical, and radio-frequency domains. The pulses are generated by a combination of passive amplitude modulation arising from nonlinear polarization evolution and passive frequency modulation due to quasi-soliton-like pulse shaping. Several distinct operation modes for ultrashort pulse generation are described and pulses as short as 38 fs are directly generated in the cavity. >

Journal ArticleDOI
TL;DR: In this paper, an efficient and low thermal impedance laser diode array heatsink is presented for high duty factor or CW operation of fully filled diode arrays made possible at high average power.
Abstract: Detailed performance results for an efficient and low thermal impedance laser diode array heatsink are presented. High duty factor or CW operation of fully filled laser diode arrays is made possible at high average power. Low thermal impedance is achieved using a liquid coolant and laminar flow through microchannels. The microchannels are fabricated in silicon using an anisotropic chemical etching process. A modular rack-and-stack architecture is adopted for the heatsink design, allowing arbitrarily large two-dimensional arrays to be fabricated and easily maintained. The excellent thermal control of the microchannel cooled heatsinks is ideally suited to pump array requirements for high average power crystalline lasers. >

Journal ArticleDOI
TL;DR: In this paper, the development of high-power diode laser arrays for solid-state laser pumping is detailed, including advances in available wavelength, efficiency, temperature of operation, duty cycle of operation and peak and average power levels or densities.
Abstract: Recent progress in the development of high-power diode laser arrays for solid-state laser pumping is detailed. Advances in available wavelength, efficiency, temperature of operation, duty cycle of operation, and peak and average power levels or densities are described. A packaging architecture capable of addressing the broadest range of pump applications and designs in an economic manner is defined, and a range of such package designs is presented. >

Journal ArticleDOI
TL;DR: In this article, an algorithm is developed that permits the direct time integration of full-vector nonlinear Maxwell's equations, which permits the modeling of both linear and nonlinear instantaneous and dispersive effects in the electric polarization in material media.
Abstract: An algorithm is developed that permits the direct time integration of full-vector nonlinear Maxwell's equations. This capability permits the modeling of both linear and nonlinear instantaneous and dispersive effects in the electric polarization in material media. The modeling of the optical carrier is retained. The fundamental innovation is to notice that it is possible to treat the linear and nonlinear convolution integrals, which describe the dispersion, as new dependent variables. A coupled system of nonlinear second-order ordinary differential equations can then be derived for the linear and nonlinear convolution integrals, by differentiating them in the time domain. These equations, together with Maxwell's equations, are solved to determine the electromagnetic fields in nonlinear dispersive media. Results are presented of calculations in one dimension of the propagation and collision of femtosecond electromagnetic solitons that retain the optical carrier, taking into account the Kerr and Raman interactions. >

Journal ArticleDOI
TL;DR: In this article, the nonlinear gain coefficient epsilon, which induces a gain grating through the pump-probe beating, is estimated to be 1.75*10/sup -23/ m/sup 3/m/sup 4.
Abstract: Nondegenerate four-wave mixing is measured in the 1.5 mu m traveling-wave semiconductor optical amplifier medium as a function of the pump-probe detuning frequency ranging from a few GHz to 400 GHz. It is found that two different sources are responsible for the four-wave mixing: the carrier density modulation and the nonlinear gain effect. The latter is clearly observed when the detuning frequency increases above 100 GHz. The nonlinear gain coefficient epsilon , which induces a gain grating through the pump-probe beating, is estimated to be 1.75*10/sup -23/ m/sup 3/. The change in the real refractive index associated with the nonlinear gain effect, which generates an index grating, is negligibly small. The relaxation time involved in the nonlinear gain effect is found to be less than 0.3 ps. These results support the role of the spectral hole burning rather than the carrier heating in the nonlinear gain effect. >

Journal ArticleDOI
TL;DR: In this paper, a femtosecond pulse shaping apparatus is used for storage, recall, and processing of femto-cond waveforms, which can be used for matched filtering, dispersion compensation, encryption and decoding and femtocond waveform synthesis.
Abstract: Storage, recall, and processing of shaped femtosecond waveforms are achieved by performing spectral holography within a femtosecond pulse shaping apparatus. Time reversal, as well as correlation and convolution, of femtosecond temporal signals is demonstrated. Applications of this technique to matched filtering, dispersion compensation, encryption and decoding and femtosecond waveform synthesis are also discussed. The work extends the powerful principles of holographic signal processing, which have been used extensively for pattern recognition and filtering of two-dimensional spatial signals, to the femtosecond time domain. >