TUESDAY zyxwv MORNING zyxw / CLEO zyx 2001 / z 111 zy nardi, H. Wenzel, B. Klein, unpublished 1999. S.P. Hegarty, G. Huyet, zyxwvutsrqpon P. Porta, J.G. McIner- ney, K.D. Choquette, K.M. Geib and H.Q. Hou, JOSA B 16,2060 (2000). E.R. Hegblom, D.I. Babic, B.J. Thibeault and L.A. Coldren, IEEE STQE 3,379 (1997). G.R. Hadley, K.L. Lear, M.E. Warren, K.D. Choquette, J.W. Scott and zyxwvutsrqpon S. Corzine, IEEE JQE 32,607 (1989). zyxwvutsrqpo CTuB7 9:30 am Optical Galn-Bandwldth Product of Vertical-Cavlty Ampliflers Joachim Piprek, E. Staffan Bjorlin, and John E. Bowers, Electrical and Computer Engineering Department, University of California, Santa Barbara, C A 93106; Email: piprek@ece.ucsb.edu Vertical-cavity semiconductor optical amplifiers (VCSOAs) have recently attracted increasing in- terest. They are potentially low-cost alternatives to in-plane SOAs and they have the inherent ad- vantage of polarization insensitivity, high fiber coupling efficiency, and low noise figure. Two-di- mensional arrays of VCSOAs are attractive for parallel applications. We have recently demon- strated the first VCSOA that operates at 1.3pm signal wavelength.' In our undoped and optically pumped device, two AlAs/GaAs distributed Bragg reflectors (DBRs) are wafer bonded to an InP based active region (Fig. 1). The active region contains three stacks of 7 compressively strained InAsP quantum wells that are placed at the three central peaks of the standing optical wave. The effective cavity length is 2.2pm including light penetration into the mirrors. The quantum wells are the only layers to allow for band-to-band ab- sorption of the 980 nm pump laser beam. Up to 13 dB fiber-to-fiber gain, -3.5 dBm saturation output power, and 0.6 nm optical bandwidth (100GHz) are measured in reflection mode.' Low optical bandwidths are desirable for filter appli- cations whereas larger bandwidths are needed for wavelength division multiplexing (WDM). Due to the trade-off between gain and bandwidth, we use here the gain-bandwidth product as figure of merit. The inset of Fig. 2 shows gain vs. signal wave- length as measured in reflection mode on a new generation of our 1.3~m VCSOAs. The zyxwvutsrq Al- GaAslGaAs front DBR is used for signal input and output, the pump beam enters through GaAs g 4.0 2 P 'E 3.5 2 2 3.0 ! GWAtAs mirror .___ GaAdAIAI mirmr j 25 ............................. 4Mo 5M)O 5500 6090 6Mo 7WO Vertical Position [nm] CXB7 Fig. 1. Refractive index profile and standing optical wave in the center of our dou- ble-fused 1.3pm vertical-cavity amplifier. 1 .XI S.".IW.".*"#h I",") 10, . . . . , . . . . , . . . .r, 0.85 0.90 0.95 Front Mirror Reflectivity CTuB7 Fig. 2. Square-root of peak gain times optical bandwidth vs. front mirror reflectivity as calculated (line) and as measured on three differ- ent devices (dots) in reflection mode. The inset illustrates the measurement on our most recent device, fiber coupling losses not included. CTuC SO0 am-9:45 am Room 341/342 Passive Guided Wave Structures and Devices Craig Siders, Univ. of Central Florida, Presider CTuCl (Invited) 8:OO am Laser wakefleld accelerators: Status and applications Wim Leemans, LBL, USA Summary not available. CTuC2 8:30 am substrate and back mirror. Multiplying the -3dB optical bandwidth (Af = 36GHz) with the square root of the maximum amplifier gain (G = 10.8 dB = 12) gives the gain-bandwidth product (124GHz) which is constant for any given device. We have derived the following simple design for- mula for the gain-bandwidth product in reflec- tion mode with the cavity refractive index nc, the effective cavity length L,, and the front mirror reflectivity Rf (c is the vacuum light velocity). Remarkably, the back mirror does not affect the result in re- flection mode. Figure 2 plots our formula vs. front mirror reflectivity (n, = 3.2). Dots repre- sent measurements on two different 1.3pm de- vices as well as on a previously fabricated 1.5pm VCSOA with Si/Si02 front mirror and 3.8pm cavity length.3 The front mirror design is the main difference between the 1.3pm devices shown. In perfect agreement with our formula, less front mirror reflectivity results in larger gain- bandwidth products. However, stronger pump- ing is required to maintain constant amplifier gain with lower reflectivity. For our reflection mode case, gain-bandwidth products above 1 THz can be achieved if the input DBR reflectivity is less than 0.86 (Fig. 2). The talk will also address transmission mode optimization. 1. S. Bjorlin, B. Riou, A. Keating, P. Abraham, Y-J. Chiu, J. Piprek, J. Bowers, Phot. Technol. Lett. 12,951 (2000). S. Bjorlin, B. Riou, P. Abraham, J. Piprek, Y-J. Chiu, K.A. Black, J. Bowers, to be published in J. Quantum Electr. R. Lewen, K. Streubel, A. Karlsson, S. Rapp, Phot. Technol. Lett. 10,1067 (1998). 2. 3. Nonlinear relativistic optics In the single- cycle, single-wavelength regime with kilohertz repetition rate G. Mourou A. Maksimchuk, 2. Chang, J. Nees, M.N. Naumova.* S.V. Bulanov,, T.Zh. Esirkepov,*" H. Ruh1,t F. Pegoraro,S Centerfor Ultrafast Optical Science, University of Michigan, Ann Arbor, MI 48109-2009, USA; Email: mourou@eecs. umichxdu; 'General Physics Institute of Russian Academy of Sciences, Moscow, Russia; Email: bulanov@ifp.mi.cnr.ic **Moscow Institute of Physics and Technology,Dolgoprudny, Russia; tMux-Born Institute, Berlin, Germany; fPisa University and Institute of Plasma Physics, Pisa, Italy Laser intensity in the relativistic regime, i.e. >IO'* W/cm' for near-IR light,' has opened new fron- tiers in physics. At this intensity, electrons acquire quiver energy greater than, 0.5 MeV, correspon- ding to the mass-energy of the electron. Their relativistic behavior is dominated by a mass in- crease and a large ponderomotive force (v x B) where v is the quiver velocity of the electrons and zyx B the light magnetic field. The laser-matter inter- action in this regime is characterized by the gen- eration of high-energy photons (x-rays and y- rays) and energetic electrons and ion. The latter are accelerated to tens of MeVs by the large forces associated with the v x B term. Until recently this regime could only be attained by large low-repe- tition-rate TLSapphire and Ndglass CPA sys- tems. Recently, we have shown' that single mili- joule pulses in the IO-fs regime (single cycle), focused to 1-pm (single wavelength), can pro- duce intensities greater than 1019W/cmZat kilo- hertz repetition rates. Because of their very short Rayleigh range (-1 pm) one might think that these pulses would have only limited applica- tions. They would not be useful in electron accel- eration, where longer interaction distances are necessary. If the laser numerical aperture (NA) is matched to the NA of a relativistic waveguide (determined by the laser power and the plasma frequency), single-mode propagation of the rela- tivistic pulse over many Rayleigh ranges can be obtained, as in conventional waveguide optics. This is demonstrated by the following 2D PIC simulation3 of laser pulse matching with a plas- ma slab. The simulation box size is 60h x 20h. An un- der-dense hydrogen plasma slab with density n =