Timing jitter reduction of silicon hybrid harmonically mode-locked ring laser using an integrated sampled-grating DBR.

An integrated sampled-grating silicon hybrid mode-locked ring laser is proposed for 20-GHz super-mode noise suppression. The dynamics, phase noise, and timing jitter are investigated using a delay differential equation (DDE) model. The results show that the 20-GHz harmonic regime of the proposed structure is significantly increased when the sampled-grating structure is included. Additionally, a better selectivity of the optical modes by a sampled-grating distributed Bragg reflector (SGDBR) leads to more suppression of super-mode noise compared to the long-ring structures with a spectral filter which were previously reported. Compared to previous works, the phase noise is improved by approximately 6 dB and the timing jitter is decreased to less than a third.

CROW-based Fano structures for all optical switching devices.

In this paper, an improved optical Fano switch based on coupled resonator optical waveguides (CROWs) is presented. The new topological design is employed to achieve steeper and highly asymmetric Fano resonances (FRs). Physically, in the proposed structures, due to the increase in the effective refractive index at the center of the CROW, a confined mode arises in the continuum background according to the variational theorem and leads to FR. The results show that in CROW-based Fano switches, the Fano spectrum is improved by tuning the number of nanocavities. The ratio between the slope ratio and linewidth shows an improvement of 55.25% from single to CROW5. As an important application of FR, an ultra-compact device with a CROW-based Fano structure is demonstrated. The results of the numerical finite difference time domain simulation agree well with the theoretical coupled mode theory.

Proposal of phase noise and jitter reduction in a long-ring hybrid silicon mode-locked laser by intracavity reflectors.

We propose a harmonically hybrid silicon mode-locked ring laser using intracavity reflectors (ICRs) to suppress supermode noise. The dynamic and noise properties of the structure are investigated using a delay differential equation model. The results of the dynamic show that a 20 GHz harmonic regime of the structure is significantly increased compared to a without intracavity-reflector structure. Additionally, the phase noise of the proposed structure (PS) is improved to about 8 dB. Furthermore, an analysis shows that timing jitter reduction has periodic behavior by changing the harmonic inter-spike interval time (TISI).

Circuit level implementation of photonic crystal devices.

Different types of photonic crystal components have been modeled by approximate RLC circuits. The proposed lumped circuits exploit the analogy of photonic crystal elements and RLC circuits. They are either coupled to each other or inserted like lumped circuits to imitate wave propagation within the photonic devices. Different examples such as side-coupled waveguide-cavity systems, side-coupled cavity-cavity systems, and improved structures are investigated for evaluating the theory. It is shown that the proposed circuits are exact enough to be substituted into the complicated calculations of numerical methods. In addition, the presented practical and straightforward procedure can be employed for flexible and efficient design. The results are verified using the finite-difference time-domain numerical simulations and coupled-mode theory for various devices.

Modeling and analysis of distributed feedback quantum dot passively mode-locked lasers.

In this paper, we investigate numerically two proposed monolithic distributed feedback quantum dot passively mode-locked lasers (DFB-QDMLLs) with and without gratings in the saturable absorber (SA) section in order to enhance two important performances of QDMLLs for ultrahigh-bit-rate and single-mode applications. We find out that depending on the length of the grating, optical pulses with durations of about 3-8 ps at approximately 2nd and 4th harmonics of cavity round-trip frequencies can be generated by the proposed structures. We also compare the temporal and spectral behaviors of these structures under specified bias conditions and SA lengths. It is shown that DFB-QDMLLs have the ability to generate optical pulses with more peak power than grating-embedded saturable absorber (GESA-DFB-QDMLL) structures which generate shorter pulses with narrower spectral bandwidths. We also show that DFB-QDMLLs operate in a larger range of absorber voltages while the other structure is very sensitive to absorber voltage and operates well for middle ranges of this parameter.