Single Microdisk Resonator Research Articles

On-chip all-optical second-order ordinary differential equation solver based on a single microdisk resonator.

This paper proposes an all-optical second-order ordinary differential equation (SODE) solver based on a single microdisk resonator. We validate the feasibility of our structure for constant and complex coefficient SODE solutions for Gaussian and super-Gaussian pulses. The results demonstrate a good agreement between the solutions obtained with the designed structure and those obtained through mathematical calculations for both constant and complex coefficient SODEs. We also discuss the influence of input optical signal pulse width on solution result deviations. Furthermore, we validate the capability of the designed structure to achieve tunable solutions for complex-coefficient SODEs with a tuning power of less than 10 mW. The device footprint is approximately 20×30 μm2, and it is 3-4 times smaller than the current smallest solving unit. The maximum Q-factor reaches 9.8×104. The proposed device avoids the traditional approach of cascading two resonators for SODE solving. Moreover, achieving mode alignment within the same resonator reduces the process challenges associated with aligning multiple devices in a cascade. Furthermore, it offers wider applicability for solving SODEs, namely, the ability to solve both constant and complex coefficient SODEs with complete derivative terms.

Scalable On‐Chip Microdisk Resonator Spectrometer

AbstractOn‐chip micro‐spectrometers are sought after with great effort owing to extensive potential applications in mobile optical sensing and imaging. By multiplexing more physical channels, the reconstructive spectrometers based on the spectral‐to‐spatial mapping technique can improve the spectral range. However, this method is challenging to implement and sustain due to the increase in system complexity and the decrease of dynamic range or spectral resolution. Here, a micro‐spectrometer utilizing a single tunable microdisk resonator (MDR) is demonstrated. Such a single MDR spectrometer has only one physical channel to receive all spectral components with a compact size, overcoming the trade‐off among spectral resolution, spectral range, and dynamic range. Leveraging the wavelength and temperature‐dependent response matrix, unknown spectra are reconstructed from their corresponding output light intensity vector. The fabricated device illustrates a high resolution of 0.01 nm for a dual peak and a medium resolution of 0.2 nm in the 20 nm spectral range. A wide variety of complex input spectra, including narrowband and broadband spectral signals, can be well recovered, exhibiting the robustness of the spectral reconstruction approach. Moreover, this proposed spectrometer exhibits ease of scalability and flexible configuration to a spectrometer array covering a set of desired and even discrete spectral ranges.

Electromagnetically induced transparency-like effect in a two-bus waveguides coupled microdisk resonator

We observe theoretically and experimentally electromagnetically induced transparency (EIT)-like effect in a single microdisk resonator (MDR) evanescently coupled with two bus waveguides. This structure is modeled using transfer matrix method, and it is revealed that the EIT-like spectrum originates from the coherent interference between two nearby low-order whispering-gallery modes (WGMs) with comparable quality factors. The EIT-like properties have been investigated analytically with respect to coupling efficiency, round-trip power attenuation, as well as phase spacing between two resonances. The resonance spacing and mode coupling are adjustable by varying the effective indices of WGMs and waveguide mode. Consequently, fully integrated MDRs were fabricated in silicon. Resonant modes and coupling efficiency are studied in one-bus waveguide coupled MDRs. Finally, EIT-like resonance is observed in a two-bus waveguides coupled MDR of 3 μm in radius with a quality factor of 4,200 and central transmission larger than 0.65. The experimental results agree with our modeling well and show good internal consistency, confirming that two WGMs coupled in a point-to-point manner are required for EIT-like effect.

Experimental observation of optical differentiation and optical Hilbert transformation using a single SOI microdisk chip

Optical differentiation and optical Hilbert transformation play important roles in communications, computing, information processing and signal analysis in optical domain offering huge bandwidth. Meanwhile, silicon-based photonic integrated circuit is one of the most promising candidates for all-optical signal processing due to its intrinsic advantages of low power consumption, compact footprint, ultra-high speed and compatibility with electronic integrated circuits. In this study, we analyze the interrelation between first-order optical differentiation and optical Hilbert transformation and then experimentally demonstrate a feasible integrated scheme which can simultaneously function as first-order optical differentiation and optical Hilbert transformation based on a single microdisk resonator. This finding may motivate the development of integrated optical signal processors.

Dual-band optical filter based on a single microdisk resonator

We propose and experimentally demonstrate a dual-band optical filter based on a single microdisk resonator. An analytical model is built based on the transfer matrix method and is applied to simulate the properties of such a device. Competition and interference of the dual modes in the resonator lead to dual-band filtering with high isolation. As the finite-difference time-domain simulation illustrates, two low-order resonant modes can be effectively triggered by optimizing the waveguide width and spacing gap between the compact resonator and waveguides. In experiment, a double side-coupled microdisk resonator was fabricated on a nanophotonic silicon-on-insulator platform, and dual-band bandpass filtering is realized with an optical isolation higher than 20 dB and an insertion loss lower than 2 dB. The experimental results agree well with our modeling results.

耦合微盘及带输出波导的单微盘腔的耦合模式特性

The optical microresonators with high Q factor and ultra-small mode volume have attracted great attentions for applications in optoelectronic devices. For a coupled-microdisks and a single microdisk connected with an output waveguide, coupled mode characteristics resulting from the structure asymmetry are investigated by the finite-difference time-domain(FDTD) method and the Pade′ approximation. Mode field patterns and mode Q factors are calculated, and the relative energies of mode-field components with different angular wave numbers are estimated from the coupled mode-field distribution. For coupled microdisk resonator, the higher-order modes introduced by the mode coupling usually reduces the mode Q factor of the coupled mode greatly. For a single microdisk resonator with a radius of1μm and a refractive index of3.2 connected with a0.2-μm-wide output waveguide, a coupled mode at the wavelength of1.52μm is observed with the mode Q factor of268 and a triangle mode-field pattern, which is the coupled mode between whispering-gallery modes TE9,1 and TE6,2 with a wavelength difference of6.6 nm.

Whispering-gallery modes and light emission from a Si-nanocrystal-based single microdisk resonator

We report on visible light emission from Si-nanocrystal based optically active microdisk resonators. The room temperature photoluminescence (PL) from single microdisks shows the characteristic modal structure of whispering-gallery modes. The emission is both TE and TM-polarized in 300 nm thick microdisks, while thinner ones (135 nm) support only TE-like modes. Thinner disks have the advantage to filter out higher order radial mode families, allowing for measuring only the most intense first order modal structure. We reveal subnanometer linewidths and corresponding quality factors as high as 2800, limited by the spectral resolution of the experimental setup. Moreover, we observe a modification of mode linewidth by a factor 13 as a function of pump power. The origin of this effect is attributed to an excited carrier absorption loss mechanism.