Evgeny A. Viktorov

Bistable regimes in an optically injected mode-locked laser

We study experimentally the dynamics of quantum-dot (QD) passively mode-locked semiconductor lasers under external optical injection. The lasers demonstrated multiple dynamical states, with bifurcation boundaries that depended upon the sign of detuning variation. The area of the hysteresis loops grew monotonically at small powers of optical injection and saturated at moderate powers. At high injection levels the hysteresis decreased and eventually disappeared.

Feedback-induced discretisation of the relaxation oscillation frequency in a semiconductor laser

We explore both experimentally and numerically the dynamics of semiconductor lasers subject to delayed optical feedback and show that the external cavity repetition rate can be resonant with the relaxation oscillations leading to a discretisation of the relaxation oscillation frequency which evolves in a series of discrete steps, remaining almost constant along each step. Numerically, the steps are found to result from different Hopf bifurcation branches.

Frequency modulated external cavity laser with photonic crystal resonator and microheater

We demonstrate frequency modulation (FM) in an external cavity III-V/Silicon laser, comprising a Reflective Semiconductor Optical Amplifier (RSOA) and an SU8 polymer waveguide vertically coupled to a 2D Silicon Photonic Crystal (PhC) cavity. Laser FM was achieved by local heating of the PhC using a resistive element of Ni-Cr metal as a microheater to change the refractive index in the cavity hence changing the lasing frequency. Presented is a thermal study of the laser dynamics and observations of the shift in lasing frequency.

Theoretical study of mode-locked lasers with nonlinear loop mirrors

We analyze the properties of a unidirectional class-A ring laser containing a nonlinear amplifying loop mirror (NALM). The NALM is a Sagnac interferometer consisting of an amplifier and a Kerr-type nonlinear element, and has a reflectivity that periodically varies with the intra-cavity power. To model the dynamics of these lasers, we use the approach based on Delay Differential Equations (DDEs) that has been successfully applied to describe the properties of passively mode-locked semiconductor lasers. The proposed model allows us to investigate mode locking operation in this laser. The analysis of this DDE model for mode-locked operation was performed numerically and analytically in the limit of large cavity round trip times. We demonstrate that mode-locked pulses are born though a modulational instability of the steady state solutions when the pseudo- continuous branch crosses the imaginary axis. These asymmetric pulses always co-exist with the stable laser-off solution. Hence, they can be viewed as temporal cavity solitons having similar properties with localized structures observed in bistable spatially-extended systems.

Optical square waves from a nonlinear amplifying loop mirror laser (Conference Presentation)

Optical square wave sources are particularly important for applications inxa0high speedxa0signal processing and optical communications. In most realizations, optical square waves are generated by electro-optic modulation,xa0dispersion engineering of mode-locked lasers,xa0polarizationxa0switching, or by exploiting opticalxa0bi-stabilityxa0and/or optical delayed feedback in semiconductor diode lasers, as well asxa0vertical-cavityxa0surface-emitting lasers (VCSELs). All such configurations are bulky andxa0cause significant timing jitters.xa0Here we demonstratexa0the direct generation of optical square waves from a polarization-maintaining figure-eight nonlinear amplifying loop mirror (NALM) configuration that uses an embedded high index glass micro-cavity as the nonlinear element.xa0Suchxa0a NALMxa0mimics the behavior of a saturable absorber and has been used to reach passivexa0mode-lockingxa0of pico- and even nano-second pulses.xa0In our method, the NALM, including a high-Qxa0micro-ringxa0resonator,xa0acts as an ultra-narrowband spectral filter and at the same time provides a large nonlinear phase-shift. Previously we have demonstratedxa0that such a configuration enables sufficient nonlinear phase-shifts for low-power narrow-bandwidth (~100 MHz FWHM) passive mode-locked laser operation.xa0Here we demonstrate the switching of stable optical square wave pulses from conventional mode-locked pulses by adjusting thexa0cavity properties.xa0In addition, the square wave signal characteristics, such as repetition rate andxa0pulse duration, can be also modified in a similar fashion. The source typically produces nanosecond optical square wave pulses with a repetition ratexa0of ~ 120 MHz atxa01550nm. In order to verify the reach of our approach, we compare our experimental results with numerical simulations using a delay differential equation model tailored for a figure-eight laser.

Q-switch in injected quantum dot laser

We report on Q-switched operation in an optically injected quantum dot laser. It results from the ability of the laser to emit simultaneously from the ground state (GS) and first excited state (ES). The injected GS operates as a gate for the ES output.

Dynamical interplay between ground and excited states in quantum dot laser

Semiconductor quantum dot lasers are attractive for multiple technological applications in biophotonics. Simultaneous two-state lasing of ground state (GS) and excited state (ES) electrons and holes in QD lasers is possible under a certain parameter range. It has already been investigated in steady-state operations and in dynamical regimes and is currently a subject of the intensive research.

Clustering phenomena in a quantum dot laser

This paper models the clustering phenomena in a quantum dot laser using a phase description suitable for a large system of globally coupled oscillators. In this model, the coupling function depends on the phase difference and includes higher Fourier. For various distributions of the unperturbed frequencies, the appearance of frequency locking regimes, clustering and antiphase dynamics are demonstrated.