Integrated CdS Singlemode Nanowire Laser


a – optical image of the hybrid structure of MZI upon excitation. b, a schematic configuration of an in-process nanowire laser. CdS nanowire is used as a gain material and is evanescently associated with? A SiN waveguide on both sides, forming a hybrid MZI structure. In the field of communications, the bends of the SiN waveguide are pre-engineered to provide high coupling efficiency with excellent reproducibility. Fiber couplers are designed for both ends of the SiN waveguide, which connect the laser signal from the integrated SiN waveguide to standard optical fibers to determine optical characteristics. c — lasing spectra obtained at various pump intensities above the threshold. The dominant generation peak is centered at a wavelength of approximately 518.9 nm with a line width of approximately 0.1 nm. The side mode suppression coefficient increases with increasing pump intensity and reaches a maximum value of about 20 times (13 dB). d is an optical image of a measuring device under an optical microscope. The measuring installation uses output fibers to collect signals from the microcircuit through the arrays of the fiber optic system. Photo: Qingyang Bao, Weijia Li, Peizhen Xu, Ming Zhang, Taooxing Dai, Pan Wang, Xin Guo and Liming Tong

In recent years, increasing attention has been paid to the integration of active nanowires with plane waveguides embedded in the crystal for embedded light sources. To achieve this, scientists in China have demonstrated a very compact single-mode cadmium sulfide (CdS) nanowire laser by integrating a stand-alone CdS nanowire into a silicon nitride (SiN) photon chip. The integration scheme on a chip will open up new possibilities for both nanowire photonic devices and light sources on a chip.


In the last decade, nanophotonics on a crystal has attracted more and more attention to the implementation of integrated photonic schemes with faster operation, wider bandwidth, lower power consumption, and higher compactness. Despite the fact that a number of nanophotonic devices and circuits on a chip have been successfully manufactured using technology compatible with metal oxide semiconductor (CMOS), the light sources on the chip remain complex. On the other hand, semiconductor nanowires grown from bottom to top have long been used for nanoscale waveguide lasers. In recent years, increasing attention has been paid to the integration of active nanowires with plane waveguides embedded in the crystal for embedded light sources. However, due to the large discrepancy in manufacturing methods, refractive indices, and geometric compatibility between an autonomous nanowire and an integrated plane waveguide, a number of problems, including relatively low coupling efficiency, inefficient mode selection, and low reproducibility, have yet to be resolved. to be addressed.

In a new article published in Light of science and applicationsScientists from the State Key Laboratory of Modern Optical Instrumentation, College of Optical Sciences and Engineering, Zhejiang University, China, demonstrated on a crystal a single-mode CdS-based nanowire laser with high coupling efficiency. The choice of mode is carried out using the structure of the Mach-Zehnder interferometer (MZI). When the pump intensity exceeds the generation threshold 4.9 kW / cm2single-mode lasing on a crystal at a wavelength of about 518.9 nm is achieved with a line width of 0.1 nm and a side mode suppression ratio of 20 (13 dB). The output signal of a nanowire laser is sent to a SiN waveguide integrated into the crystal with high efficiency (up to 58%) through a damped coupling, and the directional coupling coefficient between two output ports can be varied from 90% to 10% by preliminary designing the coupling length of the SiN waveguide. Taking advantage of the wide variety of available nanowire materials and high flexibility to create a forbidden band, the integration scheme on a chip shown here can easily be expanded to implement ultraviolet to near infrared nanolasers on a crystal, which may open up new possibilities for both semiconductor nanowires and on the chip photonic devices.

These scientists summarize the production and operation of the laser: “We use micromanipulations under an optical microscope to integrate CdS nanowires onto a SiN chip and form a hybrid MZI structure with excellent reproducibility. Using MZI to select a mode, we use the Laser in single-mode. "We can also change the output coefficients between the two ports of the MZI laser laser using different bond lengths of the waveguide bends.”

“The overall size of the MZI hybrid structure is kept below 100 microns. Fiber couplers are designed at both ends of the SiN waveguide, which connect the laser signal from the integrated SiN waveguide to standard optical fibers for an optical fiber. characteristic. "

“Comparing the generation intensities at the end of the nanowire and the grating region, we estimate that the fractional power sent to the SiN waveguide is approximately 58%, which is much higher than the previous results obtained in integrated circuits based on nanowires and can be further improved by optimizing the communication efficiency between the nanowire and SiN waveguide"they added.

“Due to the wide variety of available nanowire materials and the high flexibility to create a band gap, the integration scheme on a chip demonstrated here can easily be expanded to implement nanolasers on a crystal from ultraviolet to near infrared and on the crystal inside the crystal. single-mode nanowire laser Thus, it may provide an opportunity to developchip physical and biochemical optical sensors with higher stability and compactness, ”scientists predict.


Heterostructure and quality factor for low threshold and stable nanowire generation


Additional Information:
Qinyang Bao et al., Single-mode single-mode CdS-based laser, Light: science and application (2020). DOI: 10.1038 / s41377-020-0277-0

citation:
Integrated single-mode CdS nanowire laser (March 20, 2020)
retrieved March 20, 2020
from https://phys.org/news/2020-03-on-chip-single-mode-cds-nanowire-laser.html

This document is protected by copyright. Other than honest deals for private study or research, no
Part may be reproduced without written permission. Content is provided for informational purposes only.





Source link

Leave a Comment