Bistable Laser Research Articles

Fast manipulation of laser localized structures in a monolithic vertical cavity with saturable absorber

We show the spontaneous and controlled formation of bistable and localized laser spots in the transverse section of a monolithic vertical cavity laser with a saturable absorber. Successive incoherent writing and erasure is obtained up to 80 MHz repetition rate with a 60 ps localized excitation. We also show the formation of clusters of laser localized states. All these observations are in good qualitative agreement with existing models.

Study of the optical bistability in the laser oscillation of Yb:GdVO4 crystal

We have studied the effect of optical bistability exhibited in the laser oscillation of Yb:GdVO4 crystal, revealing the complexities arising from the coexistence and switching of σ and π polarization states characteristic of this crystal. In terms of absorbed pump power, the range for bistable operation can be in excess of 1 W, while the output power generated at the up-threshold can reach as high as 0.71 W. The studies also show significant influence of the Yb concentration, the crystal thickness, the output coupling, and the resonator configuration on the bistable laser operation.

Characterization of All-Optical Regeneration Potentials of a Bistable Semiconductor Ring Laser

All-optical pulse reamplification, reshaping (2R), and retiming (3R) using a monolithic bistable semiconductor ring laser (SRL) is demonstrated for the first time. The regeneration performance of the SRL is characterized with an all-optical settable switching threshold, achieving significant increases in the extinction ratio (ER) of the output pulse for input ER as low as 1 dB. For retiming, a rectangular retiming window generated by a clean clock signal is used to eliminate the timing jitter in the input pulse. For input pulse with peak-to-peak timing jitter as high as ~ 12% of the bit period, the timing jitter in the retimed output pulse is reduced to < 2% of the bit period. The pulsewidth of the final regenerated data can be controlled by changing the width of the retiming window. The SRL is, therefore, shown to have a hard digital performance in both amplitude and time domain suitable for all-optical 3R.

Experimental Study on Wavelength Tunability of All-Optical Flip-Flop Based on Multimode-Interference Bistable Laser Diode

We demonstrate a wavelength-tunable all-optical flip-flop (AOFF) based on a multimode-interference (MMI) bistable laser diode (BLD) with distributed Bragg reflectors (DBRs). The wavelength tuning can be achieved by the band-filling effect and the free-carrier plasma effect with carrier injections to the DBRs. The tuning range of 3.1 nm will enable flexible and reconfigurable design of future photonic integrated circuits (PICs). Since the DBR-MMI-BLD does not require cleaved facets for its operation, multiple AOFFs can be monolithically integrated on a single PIC. In addition, the device has a large operable bandwidth of wider than 34 nm, even when we tune the lasing wavelength. A dynamic flip-flop operation is also demonstrated with rising and falling times of faster than 280 and 228 ps, respectively. No waveform distortion is observed, even when we tune the lasing wavelength.

Bistability and mode interaction in microlasers

We investigate the possibility of bistable lasing in microcavity lasers as opposed to bulk lasers. To that end, the dynamic behavior of a microlaser featuring two coupled interacting modes is analytically investigated within the framework of a semiclassical laser model, suitable for a wide range of cavity shapes and mode geometries. Closed-form coupled mode equations are obtained for all classes of laser dynamics. We show that bistable operation is possible in all of these classes. In the simplest case (class A lasers) bistability is shown to result from an interplay between coherent (population-pulsation) and incoherent (hole-burning) processes of mode interaction. We find that microcavities offer better conditions to achieve bistable lasing than bulk cavities, especially if the modes are not degenerate in frequency. This results from better matching of the spatial intensity distribution of microcavity modes. In more complicated laser models (classes B and C) bistability is shown to persist for modes even further apart in frequency than in the class A case. The predictions of the coupled mode theory have been confirmed using numerical finite-difference time-domain calculations.

Synchronization of semiconductor lasers with coexisting attractors

We study synchronization of unidirectionally coupled optical bistable systems. In particular, we consider two semiconductor lasers with an external cavity, which exhibit, when isolated, coexistence of two different attractors: fixed point and chaos, fixed point and one periodic orbit, and two periodic orbits with different periods. The analysis is performed with a cross-correlation function between the master and slave laser oscillations calculated with model equations based on the Lang-Kobayashi approach. Depending on both the laser operating point and the coupling strength, different bifurcations (Hopf, period doubling, saddle node, torus, and crisis) and diverse dynamical regimes (steady state, periodicity, quasiperiodicity, bistability, and chaos) occur in the route from asynchronous motion to complete synchronization. We show some similarities and differences between synchronization of monostable and bistable lasers.

All-optical Digital Logic Gates using Bistable Semiconductor Ring Lasers

This paper demonstrates all-optical digital logic gates using bistable monolithic semiconductor ring lasers (SRLs). With the flexible multi-functional experimental setup, we have experimentally demonstrated the application of SRLs to realize logic functions including: AND, OR, NOR, XOR and all-optical non-retum-to-zero (NRZ) to retum-to-zero (RZ) format conversion. Using bistable semiconductor ring lasers to fulfil all-optical logic functions have the advantages of high output extinction ratio, low switching energy, integration and the potential logic unit in the future.

10-Gb/s Optical Buffer Memory Using a Polarization Bistable VCSEL

Optical buffer memory for 10-Gb/s data signal is demonstrated experimentally using a polarization bistable vertical-cavity surface-emitting laser (VCSEL). The optical buffer memory is based on an optical AND gate function and the polarization bistability of the VCSEL. Fast AND gate operation responsive to 50-ps-width optical pulses is achieved experimentally by increasing the detuning frequency between an injection light into the VCSEL and a lasing light from the VCSEL. A specified bit is extracted from the 10-Gb/s data signal by the fast AND gate operation and is stored as the polarization state of the VCSEL by the polarization bistability. The corresponding numerical simulations are also performed using two-mode rate equations taking into account the detuning frequency. The simulation results confirm the fast AND gate operation by increasing the detuning frequency as well as the experimental results.

Polarization-Insensitive All-Optical Flip-Flop Using Tensile-Strained Multiple Quantum Wells

We demonstrate a polarization-insensitive all-optical flip-flop based on a multimode-interference bistable laser diode. Polarization-insensitive flip-flop operation is demonstrated with the set power as low as -3 dBm, by applying 0.3% tensile strain to the multiple quantum wells gain medium. The output state of polarization is stabilized to the transverse-magnetic mode irrespective of input polarization, indicating that our device also offers a polarization-stabilizing function. Dynamic switching is achieved without waveform distortion even when the input polarization state is scrambled.

Timing Jitter Reduction by All-Optical Signal Regeneration Using a Polarization Bistable VCSEL

All-optical signal regeneration is experimentally demonstrated using a polarization bistable vertical-cavity surface-emitting laser. The retiming operation of signal regeneration is performed by using an AND gate operation and a reset operation. An optical clock pulse and input data signal are used for the AND gate operation. The timing jitter of the regenerated signal is reduced by optimizing the injection power ratio of the clock pulse and the data signal. The retiming operation is analyzed using a simple model that includes random fluctuation of the polarization switching threshold and bandwidth limitation of the response to the injection light.

Laser action from Yb3+ ions in the ferroelectric and paraelectric phases of strontium barium niobate

We report on continuous wave laser oscillation of trivalent ytterbium ions in the frequency converter Yb3+:Sr0.6Ba0.4Nb2O6 ferroelectric laser crystal. Pump induced thermal loading has been used to drive the crystal from its ferroelectric to paraelectric phase. Stable laser radiation at 1070nm was found in both phases while a bistable laser output is observed through phase transition. In addition, diffuse green (535nm) radiation was generated by self-frequency doubling of the fundamental laser radiation because of the random distribution of microferroelectric domains existing in the ferroelectric as grown crystal.

Bistability and Switching Properties of Semiconductor Ring Lasers With External Optical Injection

We investigate both analytically and numerically the switching, locking and stability properties of a bistable semiconductor ring laser subject to an external optical injection. Minimum optical power required for the injected signal at certain frequency to switch the lasing direction of a bistable semiconductor ring laser from its initially lasing direction to initially nonlasing direction is determined. Locking to the injected signal and stability of the switched laser are investigated to give an area of reliable switching operation. Correspondingly, numerical simulation has been carried out to find successful switching and stable locking region with variable injection power and frequency, and is compared with the analytical results. The region obtained from simulation coincides well with the intersection of switching, locking and stable locking regions. The relation between switching speed and parameters of injected source is also studied numerically.

Numerical modelling of lasing in microstructures

AbstractTwo methods suitable for numerical modelling of microlasers (including photonic crystal, microcavity, and random lasers) are presented. Finite‐difference time‐domain (FDTD) method and a generalized coupled mode theory are discussed in the context of microstructured resonators. The cases of one mode and two modes with near‐identical properties but different frequencies are investigated in detail. The predictions of the coupled mode model are compared to FDTD simulations of a microcavity laser based on a single defect and twin coupled defects in a photonic crystal lattice. Different regimes of the mode competition (simultaneous and bistable lasing) are analyzed. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Switchable Lasing in Multimode Microcavities

We propose the new concept of a switchable multimode microlaser. As a generic, realistic model of a multimode microresonator a system of two coupled defects in a two-dimensional photonic crystal is considered. We demonstrate theoretically that lasing of the cavity into one selected resonator mode can be caused by injecting an appropriate optical pulse at the onset of laser action (injection seeding). Temporal mode-to-mode switching by reseeding the cavity after a short cooldown period is demonstrated by direct numerical solution. A qualitative analytical explanation of the mode switching in terms of the laser bistability is presented.

Tapered grating effects on static properties of a bistable QWS-DFB semiconductor laser amplifier

Using the steady-state model based on the coupled-mode and carrier rate equations, in this paper, we analyze the effects of trapezoidal tapered gratings on the dispersive bistable characteristics of a quarter wavelength phase-shifted distributed feedback semiconductor laser amplifier (QWS-DFB-SLA). We also compare the results with those of a purely QWS-DFB-SLA. For laser amplifiers driven to yield the same unsaturated peak amplifier gain, trapezoidal taper widens the spectral range of low-threshold bistable switching and increases the on–off switching contrast. The transfer-matrix method (TMM) is utilized for the numerical simulations.

Dynamic Operation of All-Optical Flip-Flops with Distributed Bragg Reflectors for Self-Routing of 10-Gbit/s Optical Packets

We present the dynamic all-optical flip-flop (AOFF) operation of a multimode interference (MMI) bistable laser diode (BLD) with distributed Bragg reflector (DBR) mirrors, which allow single-mode lasing and on-chip integration with other waveguide devices. The DBR-MMI-BLD has been operated by 10-ns-wide optical set/reset pulse, resulting in 320 ps rising time and 470 ps falling time. Self-routing of 10 Gbit/s optical packets has also been demonstrated using the Mach–Zehnder interferometer (MZI) semiconductor optical amplifier (SOA) all-optical switch driven by the DBR-MMI-BLD AOFF. The 10 Gbit/s optical packets were switched in the optical domain by cross-phase modulation of the SOA. The extinction ratio of the all-optical switch was 8 dB, and an error-free operation was obtained with 1.8 dB power penalty.

Analysis of Dynamic Switching Behavior of Bistable Semiconductor Ring Lasers Triggered by Resonant Optical Pulse Injection

The relaxation oscillation and decay toward steady state following the switching of the lasing direction in a bistable semiconductor ring laser triggered by resonant optical pulse injection is studied theoretically using small-signal method. Analytical expressions for damping factor, relaxation oscillation frequency, and the decay time are derived. Calculation results based on the expressions derived are compared with numerical simulations, and good agreement is observed. It is shown that the dynamic behavior can be greatly improved by increasing the differential gain, photon density, optical confinement factor, and nonlinear gain compression coefficient, as well as by decreasing the photon lifetime.

Characteristics of bistable localized emission states in broad-area vertical-cavity surface-emitting lasers with frequency-selective feedback

Small-area bistable lasing spots (about $10\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ full width at half maximum) can be created at different positions within the aperture of a broad-area vertical-cavity surface-emitting laser (aperture diameter $80\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$) with frequency-selective feedback from a grating in Littrow configuration, and an additional pinhole localizing feedback to a part of the laser. Their characteristics are analyzed depending on the grating tuning, injection current, and feedback strength. These spots are considered to be good candidates for self-localized cavity solitons, if the perturbation by boundaries can be reduced using devices with larger diameter.

Integrable multimode interference distributed Bragg reflector laser all-optical flip-flops

A novel fully integrable all-optical flip-flop has been created using distributed Bragg reflector multimode interference bistable laser diodes. The single metal-organic vapor phase epitaxy regrowth offset quantum well structure active/passive integrated flip-flop lases in single mode at 1554 nm and is compatible with standard fabrication methods of InP photonic integrated circuits (PICs). All-optical reset switching through cross-gain saturation was demonstrated over a 52-nm range, at 1522-1574 nm. An optical set has been achieved with -3 dBm and optical reset with less than -5-dBm external light injection. The flip-flop will be useful for integration in PICs of future photonic systems for self-routing and optical memories or buffers.

Theoretical and experimental study of stochastic effects on polarization rotation in a vectorial bistable laser

We investigate the two-dimensional optical rotor of a weakly modulated vectorial bistable laser submitted to a single or multiple stochastic perturbations. In the Langevin-type equation of the rotor the role of an even or odd input forcing function on the system dynamics is isolated. Through these two inputs of optical and magnetic natures we verify that the stochastic resonance exists only when the periodic modulation acts on the even parity optical input. When two mutually correlated noises are simultaneously submitted to the input functions of opposite parities, we find a critical regime of the noise interplay whereby one stable state becomes noise-free. In this case, the residence time of the light vector in the noise-free state diverges which leads to a collapse of the output signal-to-noise ratio. But, in this critical regime also obtained when one noise drives both the even and odd functions, if the system symmetry is broken through an independent lever control, we can recover the switching cycle due to a new response mechanism, namely, the dual stochastic response, with a specific output signal-to-noise ratio expression. Both the theoretical analysis and the experiment show that the signal-to-noise ratio now displays a robust behavior for a large rangemore » of the input noise amplitude, and a plateau with respect to the input signal amplitude. Furthermore, we isolate an original signature of this synchronization mechanism in the residence-time distribution leading to a broadband forcing frequency range. These noise interplay effects in a double well potential are of generic nature and could be found in other nonlinear systems.« less