Edris Sarailou

Grating based electro-optic switch with azo nonlinear optical polymers

Depth grating was inscribed into nonlinear optical (NLO) polymers functionalized with azo chromophores by a simple interferometric apparatus using a continuous wave laser within the absorption bands of NLO polymer. An attenuation of more than 99.5% with a full width at half maximum of ∼1.4nm was obtained for a single grating with a length of ∼1mm. By making use of the Pockels effect, the refractive index of the poled polymer was changed, and consequently the Bragg wavelength and filter transmission shifted. An ∼0.17nm shift in an applied field of about 116V∕μm was obtained in a weakly poled material.

Fabrication of graded index waveguides in azo polymers using a direct writing technique

Fast direct writing of waveguides on polymers using low power continuous-wave lasers has been investigated. Using the cis-trans property of a functionalized sulfonated azo chromophores, we have fabricated graded index waveguides with low loss, which is due to graded index sidewalls. Fabrication is done by exposing the polymer film to a 532nm wavelength laser beam focused to about 5μm spot at the film. Losses were calculated to be 0.48±0.04dB∕cm at 830nm wavelength with no surface deformation. This technique enables us to fabricate integrated optical circuits including directional couplers, dividers, filters, switches, etc., as they are currently investigated in our laboratory.

A Linearized Intensity Modulator for Photonic Analog-to-Digital Conversion Using an Injection-Locked Mode-Locked Laser

A linearized intensity modulator for pulsed light based on an injection-locked mode-locked laser (MLL) is presented here. This has been realized by introducing a monolithic Fabry-Pérot MLL into one of the arms of a conventional Mach-Zehnder interferometer (MZI) and injection-locking it to a MLL which is the input to the interferometer. By modulating the current on the gain section or the voltage of the saturable absorber (SA) section of the injection-locked laser, one can introduce an arcsine phase response on each of the injected longitudinal modes. By combining the modulated optical comb with its unmodulated counterpart one can produce a linearized intensity modulator. The linearity of this modulator is inherent in its design and no pre- or postdistortion linearization scheme is utilized. The results of the two-tone intermodulation experiment are presented here for this modulator and a spur-free dynamic range (SFDR) of ~70 dB·Hz2/3 is achieved by modulating the voltage of the SA. The reported SFDR is limited by the noise of the MLLs. The dynamic range could be further improved by decoupling the phase modulation and amplitude modulation. The proposed and demonstrated configuration as an analog optical link with improved linearity has the potential to increase the performance and resolution of photonic analog-to-digital converters (ADCs).

Add/drop filter using in-plane slanted gratings in azo polymers

We have fabricated in-plane slanted gratings on azo-functionalized polymeric films using a fast, direct-writing method. By properly adjusting the resonance, these gratings can be used as 90 degrees integrated reflectors and add/drop filters in the plane of the film. We have produced an attenuation of 14.8 dB at 1560.2 nm with a FWHM of 6.47 nm. Also, a signal of 1548 nm wavelength was added to the output from a different direction. Any light shifted from the resonance will pass through the filter undisturbed.

Optical and RF stability transfer in a monolithic coupled-cavity colliding pulse mode-locked quantum dot laser

We report a novel quantum dot based laser design where a stable high-Q master laser is used to injection lock a passively mode-locked monolithic colliding pulse slave laser. Coupling between the crossed orthogonal laser cavities is achieved through a common monolithically integrated saturable absorber, which results in the locking and hence reduction of the timing jitter as well as the long-term frequency drift of the slave laser. A stable 30 GHz optical pulse train is generated with more than 10 dB reduction in the RF noise level at 20 MHz offset and close to 3 times reduction in the 10 dB average optical linewidth of the slave laser.

Towards linear interferometric intensity modulator for photonic ADCs using an injection locked AlInGaAs quantum well Fabry-Pérot laser

A monolithic AlInGaAs quantum well Fabry-Pérot laser injection locked to a passively mode-locked monolithic laser is presented here. The FP laser cavity can be used as a true linear interferometric intensity modulator for pulsed light.

All Optical Stabilization of a Monolithic Quantum Dot Based CPM Laser Via Four-Wave Mixing

We investigate and confirm a four-wave mixing (FWM) process as the primary mechanism responsible for locking and stabilization of a previously reported novel quantum dot based monolithically coupled colliding pulse mode-locked (CPM) laser. In the previous letter, a high-Q passively mode-locked ring laser is used to injection lock an orthogonally coupled passively mode-locked CPM slave laser via FWM in the common saturable absorber. In this letter, we setup an experiment to verify the FWM process, whereby the external ring laser is operated unidirectionally while simultaneously analyzing the amplified spontaneous emission from the other facet of the ring laser. The emission is found to contain CPM light only in the presence of injection locking proving the FWM process. Other linear scattering effects are also investigated and shown to be negligible in the orthogonal waveguide configuration.

Injection-locked semiconductor laser-based frequency comb for modulation applications in RF analog photonics

A linearized intensity modulator for periodic and pulsed light is proposed and demonstrated. The free carrier plasma effect has been used to modulate the refractive index of the phase section of a three-section mode-locked laser. If injection locked, the modulation induces an arcsine phase response on the three-section mode-locked laser. By introducing this mode-locked laser into a Mach-Zehnder interferometer biased at quadrature, one can realize a true linear intensity modulation. This novel laser suppresses any unwanted amplitude modulation and increases the performance of the linearized intensity modulator. Experimental results have provided a record low static Iπ of 0.39 mA and a spur-free dynamic range of 75  dB.Hz2/3.

High-Q Transfer in Nonlinearly Coupled Mode-Locked Semiconductor Lasers

A novel four-wave mixing-based injection locking method was demonstrated earlier, whereby the optical and RF stability of a mode-locked high-Q ring laser is successfully transferred to an orthogonally coupled colliding pulse mode-locked (CPM) laser. Four-wave mixing in the common monolithically integrated saturable absorber is used to couple the crossed laser cavities, which is confirmed by the reduction in RF noise level and by the optical linewidth reduction of the lasing modes of the slave CPM laser. The four-wave mixing process was then further investigated and experimentally shown to be the primary mechanism responsible for the locking and stabilization of the slave laser. This paper discusses the above four-wave mixing technique in detail and presents an improved design by employing optical subharmonic hybrid mode-locking and by decreasing the losses inside the master ring cavity. The resulting higher stability of the master laser translates into further improvement in the RF and optical linewidths of the injection locked slave CPM laser. These results demonstrate the effectiveness of the novel method for all on-chip stability transfer in the forthcoming all monolithic optical pulse source systems.

Four-wave mixing mediated stabilization of an orthogonally coupled monolithic CPM laser

We experimentally confirm four-wave mixing process as the dominant mechanism responsible for injection locking in case of a novel monolithically integrated orthogonally coupled colliding pulse mode-locked (CPM) laser.