Sandor Furst

Unidirectional Bistability in AlGaInAs Microring and Microdisk Semiconductor Lasers

We report on room-temperature continuous-wave operation and single-mode lasing of microdisk and microring lasers with radii as small as 7 mum. The waveguide sidewall roughness was minimized by an optimized fabrication process using hydrogen silsesquioxane e-beam resist and Cl 2-CH 3-H 2 inductively coupled plasma etching. The devices show unidirectional bistability between the counterpropagating modes for radii larger than 30 mu m and a strong hybrid output polarization for radii smaller than 15 mum with a transverse-magnetic component of approximately 30%.

Cavity-Enhanced Four-Wave Mixing in Semiconductor Ring Lasers

We report on cavity-enhanced four-wave mixing (FWM) in 1.55-mum semiconductor ring lasers (SRLs). External optical injection into one of the cavity modes of the ring laser induces a FWM signal up to detuning frequencies of 1.5 THz. Mode-locked signals at 34.5 GHz with a linewidth as small as 5 kHz were measured. Initial results show similar characteristics with a distributed feedback laser monolithically integrated next to the SRL.

Modal structure, directional and wavelength jumps of integrated semiconductor ring lasers: Experiment and theory

We have experimentally and theoretically analyzed the modal properties of semiconductor ring lasers and the wavelength jumps that occur in connection with directional switching above the threshold.

Fast and Digitally Wavelength-Tunable Semiconductor Ring Laser Using a Monolithically Integrated Distributed Bragg Reflector

We report on a semiconductor ring laser that uses a monolithically integrated external distributed Bragg reflector section to achieve fast and digital wavelength tuning. Switching times of 450 ps and a sidemode suppression ratio exceeding 30 dB were measured.

Optically Triggered Monostable and Bistable Flip-Flop Operation of a Monolithic Semiconductor Ring Laser

A monolithic semiconductor ring laser (SRL) is demonstrated to operate as an optical monostable and bistable that can be triggered by an optical pulse, showing potential for all-optical 2R regeneration and all-optical Flip-Flop applications.

Dynamic operation of all-optical Flip-Flop based on a monolithic semiconductor ring laser

A monolithic semiconductor ring laser (SRL) is demonstrated as a fully all-optical flip-flop that can be triggered by optical pulses of 400 ps duration, showing 130 ps response time.

All-optical label swapping using bistable semiconductor ring laser

A semiconductor ring laser all-optical flip-flop is used to realize all-optical label swapping. Old address is erased by blocking the switching optically and new address is inserted by modulating the output from SRL.

Technological challenges for CW operation of small-radius semiconductor ring lasers

Theoretical investigation and device measurements are reported to demonstrate the strict fabrication requirements of small diameter shallow etched semiconductor ring lasers. A very accurate control over the dry etching depth is crucial to both minimise the bending losses and achieve very precise control of the coupling ratio in directional couplers. A reactive ion etching process was developed on Aluminium-quaternary wafer structures, showing selectivity greater than 30 between the AlInAs core layer and the InP upper cladding. The process proved very effective in providing a complete and controllable etching of directional couplers with 500nm wide gaps. Assessment on the effect of the bending losses and on the minimum ring radius was performed through characterisation of half ring lasers. A minimum current threshold of 34mA is reported on 150μm ring radius devices emitting at 1300nm.

Monolithic integration of semiconductor ring lasers with distributed Bragg gratings

Monolithic integration of 1.55-mum ring lasers with distributed Bragg reflectors (DBRs) and distributed feedback DFB lasers are presented. Such configurations show potential for mm-wave generation, wavelength tunability and are attractive for nonlinear dynamics studies in semiconductor lasers.

Time-domain response to ps optical pulse trigger of an all-optical flip-flop based on semiconductor ring laser

Monolithic Semiconductor Ring Lasers (SRLs) are promising devices for all-optical memory and all-optical switching applications, as they can operate in a directional bistable regime where only one directional mode (clockwise or anti-clockwise) is active at one time. The unidirectional bistable regime can be naturally associated to a binary logic, and the SRL represents an elementary digital memory cell that can be written all-optically, realising the function of an all-optical flip-flop. In fact, the direction of operation can be switched by injecting an external optical signal pulse into the SRL through one of the 4 input/output ports. Directional switching of the SRL-based all-optical flip-flop has been demonstrated by injecting optical pulses with 5 ps duration into one of the four input/output ports. The required switching energy is around 100 fJ, and the swiching time is between 100 and 200 ps. The same function has been demonstrated by injecting 400 ps pulses as optical trigger.