Semiconductor quantum well based shutters for NIR laser mode-locking with ∼ GHz repetition rate

Fast semiconductor shutters based on coupled wells were designed in the search for reliable, compact and cheap key element of GHz repetition rate NIR lasers passive mode-locking. Stable 0.98 GHz repetition rate 200-fs Yb:KYW laser pulses were demonstrated for SESAM including semiconductor reflector and a layer of quantum wells. The damage threshold estimate for the SESAM is ∼ 8.87 mJ/cm2. Other type of shutter – DSAM – was developed with dielectric reflector and the layer of quantum wells transferred over reflector. The measured recovery time was about 2-3 ps for both types of saturable absorbers. The efficiency relative to the incident pump power was 57% for the SESAM and 19% for the DSAM. Average output power of 2.54 W for the all-semiconductor shutter (SESAM) and of 0.92 W for the dielectric mirror with a saturable absorber (DSAM) were obtained. Actual state of the art for the shutters design is considered.

The Influece of The Laser on Acoustic Phonon Amplification in Parabolic Potential Well

We present a theoretical study of the kinetic equation for acoustic phonons in semiconductor quantum well with parabolic potential well under intense laser field. Using this method, we find the expression for the phonon rate coefficient for the general case, the condition of the acoustic phonon rate and the influence of the parameters of laser on this rate coefficient. We numerically calculate the rate of acoustic phonon excitation by the absorption of laser field energy at different temperature.

Edge states of Floquet–Dirac semimetal in a laser-driven semiconductor quantum-well

Band crossings observed in a wide range of condensed matter systems are recognized as a key to understand low-energy fermionic excitations that behave as massless Dirac particles. Despite rapid progress in this field, the exploration of non-equilibrium topological states remains scarce and it has potential ability of providing a new platform to create unexpected massless Dirac states. Here we show that in a semiconductor quantum-well driven by a cw-laser with linear polarization, the optical Stark effect conducts bulk-band crossing, and the resulting Floquet-Dirac semimetallic phase supports an unconventional edge state in the projected one-dimensional Brillouin zone under a boundary condition that an electron is confined in the direction perpendicular to that of the laser polarization. Further, we reveal that this edge state mediates a transition between topological and non-topological edge states that is caused by tuning the laser intensity. We also show that the properties of the edge states are strikingly changed under a different boundary condition. It is found that such difference originates from that nearly fourfold-degenerate points exist in a certain intermediate region of the bulk Brillouin zone between high-symmetry points.

Electrorefraction beyond the excitonic resonance in GaAs/AlGaAs multiple quantum well structure in the Franz-Keldysh geometry

The Kramers-Kronig relations were used to estimate electrorefractivity near the edge of the exciton absorption peak of GaAs/AlGaAs photorefractive quantum well (PMQW) structure working in the Franz-Keldysh geometry. It was shown that for both TE and TM polarizations the change of the refractive index under an applied electric field is at least an order of magnitude greater than in bulk semi-insulating GaAs due to the classical Franz-Keldysh effect. Full Text: PDF ReferencesD.D. Nolte, M. R. Melloch in: Photorefractive effects and Materials, ed. by D. D. Nolte (Kluwer, Dordrecht 1995). CrossRef T. E.Van Eck, L. M. Walpita, W.S.C. Chang, H. H. Wieder, "Franz–Keldysh electrorefraction and electroabsorption in bulk InP and GaAs", Appl. Phys. Lett. 48, 451 (1986). CrossRef P.K. Basu, Theory of Optical Processes in Semiconductors, (Oxford University Press, 2003) ch. 7. CrossRef A Partovi. E.M. Garmire, "Band‐edge photorefractivity in semiconductors: Theory and experiment", J. Appl. Phys. 69, 6885 (1991). CrossRef J. S. Weiner, D. A. B. Miller, D. S. Chemla, et. al. "Strong polarization‐sensitive electroabsorption in GaAs/AlGaAs quantum well waveguides", Appl. Phys. Lett. 47, 1148 (1985). CrossRef D. S. Chemla, D. A. B. Miller, "Room-temperature excitonic nonlinear-optical effects in semiconductor quantum-well structures", JOSA A, 2 1155, (1985). CrossRef S.L. Chuang, Physics of Photonic Devices (2-nd ed. New Jersey, Wiley & Sons 2009), ch. 14. DirectLink E. Miśkiewicz, A. Ziółkowski, M. Wichtowski, E. Weinert - Rączka, "Thermally induced changes of the electro-optical properties of semi-insulating GaAs/AlGaAs multiple quantum well structures", Opt. Mat. 89, 231 (2019). CrossRef E.Weinert-Rączka, R.Iwanow, "Asymetric directional coupler controlled by photorefractive grating", Acta Phys. Pol. A 95, 813 (1999). CrossRef

Edge states of Floquet-Dirac semimetal in a laser-driven semiconductor quantum-well

Band crossings observed in a wide range of condensed matter systems are recognized as a key to understand low-energy fermionic excitations that behave as massless Dirac particles. Despite rapid progress in this field, the exploration of non-equilibrium topological states remains scarce and it has potential ability of providing a new platform to create unexpected massless Dirac states. Here we show that in a cw-laser driven semiconductor quantum-well, the optical Stark effect conducts bulk-band crossing, and the resulting Floquet-Dirac semimetallic phase supports an unconventional edge state in the projected one-dimensional Brillouin zone. Further, we reveal that this edge state mediates a transition between topological and non-topological edge states that is caused by tuning the laser intensity. The existence of the respective edge states and the related topological numbers are understood in a unified manner in terms of the laser-induced polarization reflecting parity hybridization in the bulk Brillouin zone.