Lutfollah Maleki

Tunable delay line with interacting whispering-gallery-mode resonators

We theoretically study a parallel configuration of two interacting whispering-gallery-mode optical resonators and show a narrowband modal structure as a basis for a widely tunable delay line. For the optimum coupling configuration the system can possess an unusually narrow spectral feature with a much narrower bandwidth than the loaded bandwidth of each individual resonator. The effect has a direct analogy with the phenomenon of electromagnetically induced transparency in quantum systems for which the interference of spontaneous emission results in ultranarrow resonances.

Microtorus: a high-finesse microcavity with whispering-gallery modes.

We demonstrate a 165-mu;m oblate spheroidal microcavity with a free spectral range of 383.7 GHz (3.06 nm), a resonance bandwidth of 23 MHz (quality factor Q approximately 10(7)) at 1550 nm, and finesse F>/=10(4) . The highly oblate spheroidal dielectric microcavity combines a very high Q factor, typical of microspheres, with a vastly reduced number of excited whispering-gallery modes (by 2 orders of magnitude). The very large free spectral range in this novel microcavity-a few hundred gigahertz instead of a few gigahertz as in typical microspheres-is desirable for applications in spectral analysis, narrow-linewidth optical and rf oscillators, and cavity QED.

Whispering-gallery-mode-resonator-based ultranarrow linewidth external-cavity semiconductor laser

We demonstrate a miniature self-injection locked distributed-feedback laser using resonant optical feedback from a high-Q crystalline whispering-gallery-mode resonator. The linewidth reduction factor is greater than 10,000, with resultant instantaneous linewidth of less than 200 Hz. The minimal value of the Allan deviation for the laser-frequency stability is 3 x 10(-12) at the integration time of 20 micros. The laser possesses excellent spectral purity and good long-term stability.

Whispering gallery mode based optoelectronic microwave oscillator

Abstract Properties of the optoelectronic microwave oscillator (OEO) based on an optical whispering gallery mode lithium niobate disc cavity are studied theoretically. We show that the threshold of the oscillation of this device may be as low as 1 mW, and its frequency stability (Allan deviation) may be as small as 10−15/t 1/2 for reasonable experimental conditions. The properties of resonant and non-resonant OEOs are compared. Preliminary experimental results on the whispering gallery mode OEO are reported.

Generation of near-infrared frequency combs from a MgF₂ whispering gallery mode resonator.

We report on generation of a 20 nm wide, 35 GHz repetition rate optical frequency comb in a magnesium fluoride whispering gallery mode resonator pumped with 2 mW of 1543 nm light. The high efficiency of comb generation is associated with the small anomalous group velocity dispersion of the resonator. Growth dynamics of the comb is studied and compared with earlier theoretical predictions.

Sub-microwatt photonic microwave receiver

We report efficient photonic reception of nanowatt microwave signals by their direct upconversion into optical domain using high-Q whispering gallery modes in a millimeter size toroidal cavity fabricated from LiNbO/sub 3/.

Normal group-velocity dispersion Kerr frequency comb

We show via numerical simulation that Kerr frequency combs can be generated in a nonlinear resonator characterized with normal group-velocity dispersion. We find the spectral shape of the comb and temporal envelope of the corresponding optical pulses formed in the resonator.

Tunable optical single-sideband modulator with complete sideband suppression

We report on the development of a new class of widely tunable resonant single-sideband electro-optical modulators based on interaction of different mode families of a crystalline whispering gallery mode resonator with an externally applied rf field. The tunability comes from the different response of mode families to either the temperature change or the voltage applied to the resonator.

Parametric oscillations in a whispering gallery resonator

We demonstrate strongly nondegenerate optical continuous-wave parametric oscillations in crystalline whispering gallery mode resonators fabricated from LiNbO3. The required phase matching is achieved by geometrical confinement of the modes in the resonator.

On excitation of breather solitons in an optical microresonator

We theoretically investigate mode-locked regimes of optical-frequency combs generated in a nonlinear ring microresonator pumped with continuous-wave light. We find that breather solitons can be formed in the resonator for certain values of frequency and power of the pump. We argue that relatively slow modulation of the comb-frequency harmonics observed in several recent experiments can be attributed to soliton formation.