Power scaling in large-area quantum cascade lasers (QCLs) often leads to a degradation of beam quality and the emission of multi-lobed far-field patterns. In this study, we present a tapered QCL array featuring an integrated Talbot cavity on one side of the array, employing a diffraction coupling scheme. By controlling the Talbot length to one-half the Talbot distance (Zt/2), phase mode operation can be selectively achieved. Optimized in-phase mode operation is attained through careful adjustment of the Talbot cavity length. The far-field radiation pattern for in-phase operation comprises five lobes, with a central maximum lobe exhibiting a half-maximum width of 4.8°, accompanied by four side lobes. The separation between adjacent lobes measures approximately 14.3°. Ongoing research efforts are crucial to achieving enhanced beam performance and minimizing optical losses associated with integrated Talbot cavities.
We propose a high-order microring filter structure based on the Silicon-On-Insulator (SOI) platform for flattening filtering. This filter structure can achieve a box-like spectral response with large free-spectral-range (FSR) and high out-of-band extinction ratio (ER), which can be widely used in various fields, especially in the wavelength division multiplexing. The filter consists of two or more rings which are connected in series, with Ti electrodes added on them for thermal tuning. According to the proposed requirements of spectral bandwidth and FSR, the physical dimensions of the high-order microring filter structure can be calculated based on theoretical formulas, and we optimize them for better performance. The relationship of the coupling coefficients of each coupling zone is calculated based on the Butterworth spectral responses. Result shows that the higher-order filter has steeper rise-fall edges and a flatter top, and can be designed to achieve a larger FSR. The FSR of the fourth-order microring filter can be designed to 78.4 nm, with ER of 12.6 dB, and the insertion loss of 1.1 dB. The fluctuations at the top of the box-like spectra caused by the fabrication deviations can be compensated by applying voltages to Ti electrodes, which can change the effective refractive index of the waveguide.
A highly sensitive integrated optical sensor based on cascaded polarization convertor and slot waveguide microring resonator is proposed. The structure consists of an edge coupler, slot waveguide microring resonators and a reflective polarization converter. One polarization input light of the through-port of the slot waveguide microring resonator is converted into the other polarization mode after passing through the reflective polarization converter, and is coupled into slot waveguide microring resonators again. The output light of the sensor is the cascaded through-port spectrum of two different polarizations. The power conversion efficiency of the reflective polarization converter is optimized to 80%. The free spectrum ranges of the two polarization modes are different to produce the Vernier effect. Thus, the sensitivity of the sensor increases dramatically. The theoretical sensitivity of our system is 21150 nm/ Refractive-Index-Unit (RIU) with the measurement range of 0.0007 RIU. This structure has great potential in biological recognition and chemical analysis.
A higher-sensitivity optical sensor based on cascaded double-ring resonators (CDRR) for intensity interrogation has been demonstrated. By detecting the output optical power ratio between the drop port and coupling port and reducing the free spectral range for difference (ΔFSR), the intensity interrogation sensitivity of the CDRR sensor can be improved by 2.15 times.
A high-sensitivity optical sensor based on a Fabry–Pérot interferometer (FPI) has been demonstrated. The cavity of the FPI is formed by two parallel half-reflective film-coated glass substrates with a distance of 1 mm and works as the sensing area. The interaction between the propagating wave and the analyte gives the sensing signal. High sensitivity of 1149 nm / RIU has been achieved for the wavelength interrogation. The Fabry–Pérot sensor can be made into a large array with multiple microfluidic channels to detect the different types of analytes. It has great potential in biochemical sensing.
It is a tradeoff between bandwidth and resolution for the on chip Fourier transform spectrometer. To solve this problem, a single ring filter enhanced on chip Fourier transform spectrometer was proposed recently. In this paper, the performance of the cascaded double-ring enhanced Fourier transform on chip spectrometer was investigated theoretically. The cascaded two tunable Micro-ring resonators forms a large narrow band filter with a larger free spectral range (FSR) than the single ring, which reduces the requirement of the Fourier transform spectrometer spectral resolution. The spectrum of the input is retrieved by the Fourier transform algorithm with dispersion correction. The cascaded doublering enhanced Fourier transform spectrometer has a high resolution (0.3 nm) and a large bandwidth (1500nm-1600nm). The fabrication process is compatibility with CMOS process. It can be easily integrated with other silicon-based optical devices.
Although the cascaded double ring sensor can improve the sensitivity due to the difference between the radii of the reference ring and the sensing ring to produce Vernier effect, a large bandwidth spectrometer or a large tunable range laser is required for the wavelength interrogation. In this paper, the cascaded double ring senor based on silicon on insulator (SOI) with thermo-optical tuning for refractive index sensing is investigated. The peak wavelength shift of the transmission envelope can be converted into the electric power change of the micro-heater. The sensitivity reaches 33.703×103 mW/RIU by fitting Gaussian function to the spectral envelope for the wavelength interrogation with 7.9 nm wavelength measurement range.
In this paper, we compare the sensing sensitivity, the stability and the temperature sensitivity of the micro-ring resonator optical sensor based on silicon waveguide and silicon nitride waveguide. For the silicon waveguide and silicon nitride waveguide single ring, the sensing sensitivities are 1113nm/RIU and 182.64nm/RIU, the resonance wavelength variations are ±12.5pm and ±7.5pm in an hour testing at the ambient temperature and the temperature sensitivities are 0.038nm/K and 0.018nm/K, respectively. . The sensing sensitivity can be improved to 6080.6nm/RIU by cascaded double silicon nitride waveguide rings to produce Vernier effect.
We introduce an integrated polarization detection structure consisting of a photoelectric conversion material, silicon (Si), in the form of a wire grid and an aluminum (Al) wire grid polarizer layer. This structure provides transverse magnetic (TM) polarization absorptivity and an enhanced extinction ratio in the visible spectrum. Finite difference time domain simulations were used to examine the influences of different periods and thicknesses of the Si and Al grid components. The results showed that the absorptivity of TM polarization exceeded 70% in the visible spectrum (a 20% improvement), the absorptivity of transverse electric polarization was reduced by >90 % , and the extinction ratio improved by a factor of 33. When the incidence angle is over the range of 0 deg to 30 deg, the absorptivity of TM polarization and the extinction ratio perform well, exceeded 60% and 75.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.