Marco Zanola

Post-Growth Fabrication of Multiple Wavelength DFB Laser Arrays With Precise Wavelength Spacing

The design and experimental characterization of sidewall-etched gratings in III-V material fabricated with a post-growth technique are presented. The successful demonstration of an array of sidewall-etched distributed feedback lasers shows that this technology allows for a very accurate control of the wavelength spacing and a sidemode suppression ratio up to 60 dB.

Monolithically Integrated DFB Lasers for Tunable and Narrow Linewidth Millimeter-Wave Generation

A monolithic optoelectronic device for the generation of tunable and narrow linewidth millimeter-wave signals is presented. The device consists of three mutually injected distributed feedback lasers whose emission frequencies are stabilized via a four-wave mixing process. Their beating on a high-speed photodetector generates a narrow linewidth electrical signal that is continuously tunable over several tens of gigahertz.

All-Optical Directional Switching in Bistable Semiconductor-Ring Lasers

We investigate the operation of directionally bistable semiconductor-ring lasers as all-optical flip-flops. We demonstrate fast switching between the two lasing directions by injection of optical pulses acting as set and reset control signals with switching times as fast as 20 ps, delay times as short as 60 ps, and switching energy of 150 fJ.

Ultrashort Q-switched pulses from a passively mode-locked distributed Bragg reflector semiconductor laser

A compact semiconductor mode-locked laser (MLL) is presented that demonstrates strong passive Q-switched mode-locking over a wide range of drive conditions. The Q-switched frequency is tunable between 1 and 4 GHz for mode-locked pulses widths around 3.5 ps. The maximum ratio of peak to average power of the pulse-train is >120, greatly exceeding that of similarly sized passively MLLs.

All-optical Set-Reset Flip-Flop based on semiconductor ring laser: Ultrafast response and error-free Bit-Error-Rate operation

A monolithic semiconductor ring laser (SRL) operates as all-optical Flip-Flop. We report on ps-scale temporal response and Bit-Error-Rate experiments.

Generation of Picosecond Pulses Over a 40-nm Wavelength Range Using an Array of Distributed Bragg Grating Mode-Locked Lasers

A set of distributed Bragg Reflector mode-locked semiconductor lasers are presented that generate picosecond pulses over a spectral range of 40 nm on a single chip. The same technology is used to realize an integrated laser with two separate Bragg gratings coupled into a common gain and saturable absorption section. This laser is shown to lock together the two spectral slices from each grating in a single pulse train.

Monolithic All-Optical Set-Reset Flip-Flop Operating at 10 Gb/s

A monolithic semiconductor ring laser is operated as an all-optical set-reset flip-flop triggered by external optical pulses. Bit-error-rate measurements of set-reset switchings under the injection of a pseudo-random-bit-sequence have been performed, showing reliable operation up to 10 Gb/s.

Continuously tunable, narrow linewidth mm-wave generation from a monolithically integrated triple DFB laser chip

Summary form only given. Generation of stable and tunable mm-wave and THz signals is extremely attractive for applications including tomography, gas sensing and imaging for security systems. Currently photonic methods for generating signals at these frequencies show either very limited tunability, as in the case of passively mode-locked lasers and THz quantum cascade lasers , or poor spectral purity, evinced in the photomixing of two uncorrelated laser sources. In addition, current systems using the combination of a number of discrete optical elements require the use of bulky alignment optics increasing packaging costs and sensitivity to environmental noise sources. In this work a relatively simple arrangement of three DFB laser sources on a single chip is proposed and demonstrated, a schematic of the scheme is shown in Fig. 1(a). Two lasers DFB1 and DFB2 inject into DFB3 whose free running frequency is designed to emit between those of DFB. The result is that Four Wave Mixing (FWM) products of the pairs of lasers DFB and DFB are produced within DFB. These FWM signals then produce feedback signals that coincide in frequency with the complimentary laser source, i.e. the laser pair DFB produce a FWM product equal in frequency to DFB, thus locking their phases and stabilising the optical beating signal. Furthermore, by simply tuning the frequency spacing of DFB and DFB, ensuring that DFB tracks their centre point, the generated beating signal can be continuously tuned over a wide frequency range. This scheme was fabricated on a multi-quantum well AlGaInAs\InP material system and the DFB lasers were defined using upper-cladding sidewall modulation gratings in order to generate precise spacing of the three laser wavelengths [3]. Tuning of the laser wavelengths was achieved by direct current injection variation, with integrated SOA sections ensuring the optimal injection amplitude range was maintained. Measurements of the RF signal generated by the beating signal from the output at DFB show a linewidth reduction of an order of magnitude (to 2.5MHz) when the system is in the phase locked condition. Locking range measurements show a tolerance of ~2GHz on the position of the wavelength of DFB. Furthermore, the locked frequency can be tuned continuously from a few GHz to 40GHz (the maximum measureable frequency of our RF spectrum analyser) as shown in Fig.1 (b).

Integrated optically isolated laser source via non-reciprocal counter-propapagating four-wave mixing

Optical isolators based on non-reciprocal optical elements are crucial to protect laser sources from unwanted back-reflections. Commercial optical isolators are built using bulk components and micro-optics technology, and contribute a large fraction of the overall manufacturing cost of a telecom laser. Despite the impressive development in photonic integration techniques, the integration of non-reciprocal elements within conventional optoelectronic platforms, such as III-V semiconductors, is still a major challenge. So far, only a few schemes for integrated optical isolators have been actually fabricated and tested, including hybrid integration of magneto-optical materials [1], non-reciprocal mode conversion and non-reciprocal phase shift, high-speed cascaded phase-modulation [2]. Each of the above solutions has specific drawbacks, such as large insertion loss, low isolation, large size.

Semiconductor mode-locked lasers: Harnessing the gain bandwidth

A set of passively mode-locked Distributed Bragg Reflector lasers on a single chip, are shown to exhibit stable mode-locking across a 40nm bandwidth. Integration of two gratings in a single device shows dual band locking.