Desmond Lim

Finesse enhancement in silicon-on-insulator two-ring resonator system

We demonstrate experimentally the finesse enhancement in a pair of mutually coupled ring resonators coupled to two buses fabricated in silicon-on-insulator technology, as proposed theoretically in an earlier paper. A finesse close to 100 (or Q=30000) is obtained in a two-ring system, with the outer ring double the size of the inner ring, and an external coupling coefficient of 34%. The maximum finesse enhancement relative to the single-ring structure is 14 times, in good agreement with the theoretical prediction.

Timing-jitter reduction of passively mode-locked fiber laser with a carbon nanotube saturable absorber by optimization of cavity loss

We investigate the relationship between timing jitter and cavity loss of a passively mode-locked fiber ring laser with a carbon nanotube as a saturable absorber. It is the first time that we experimentally demonstrated the reduction of timing jitter by properly increasing laser cavity loss. The lowest timing jitter is achieved when the cavity loss is optimized. Theoretical analysis is in agreement with the experimental observations on the effect of cavity loss for the reduction of timing jitter. Moreover, it is experimentally shown that, at an optimal value of cavity loss, the timing jitter is reduced significantly by 24%, while the relative intensity noise increased by 4% only.

Proposal for an Ultranarrow Passband Using Two Coupled Rings

We demonstrate theoretically that a simple two-coupled-ring structure yields very narrow resonances in the transmission spectra, provided the loss is very small. The linewidth is smallest when the path lengths of the two rings have a ratio of two. Relative to the single ring, the linewidth is reduced beyond the size scaling by the intensity buildup factor in the second ring. In the lossless case, the linewidth can be two orders of magnitude narrower. The enhancement can still be seen for experimentally demonstrated silicon-on-insulator microrings.

The Transmission Properties of One-Bus Two-Ring Devices

We propose and demonstrate a simple one-bus two-ring configuration where the two rings are mutually coupled that has advantages over the one-ring structure. Unlike a one cavity system, it can exhibit near critically-coupled transmission with a broader range of loss. It can also significantly enhance the cavity finesse by simply making the second ring twice the size of the bus-coupled one, with the enhancement proportional to the intensity buildup in the second ring.

Multiple Dual-Wavelengths Erbium-Doped Fiber Ring Laser Using a Polarization-Maintaining Fabry–PÉrot Filter

A multiple dual-wavelengths erbium-doped fiber laser is demonstrated. It is designed by using a narrowband polarization-maintaining Fabry–PÉrot filter in a ring cavity. More than 30 power equalized dual-wavelengths are achieved in a 10-nm range. The switchability from multiple dual-wavelengths to normal multiple wavelengths laser is also demonstrated experimentally.

Experimental verification of finesse enhancement scheme in two-ring resonator system

We propose a finesse enhancement scheme by a simple two-ring system, in which the resonance finesse is dependent on the relative intensity buildup of the second ring with respect to the first. In lossless case, it is possible to obtain finesse two orders of magnitude higher than that of the single ring system. The two-ring system is fabricated in silicon-on-insulator using deep UV (DUV) lithography and shown to exhibit the finesse of 100 to 300. The associated finesse enhancement of 20 is in a good agreement with the theory.

A novel antenna based on confined planar helix

This paper proposes a new type of radiating structure based on confined planar helix (CPH). The structure supports surface waves and radiates in end fire direction with a small side lobe in the backfire direction. The paper describes the configuration of the radiating structure and presents simulated as well as measured radiation patterns.