Mixed-dimensional stacked nanocomposite structures for a specific wavelength-selectable ambipolar photoresponse

Mixed-dimensional composite structures using zero-dimensional(0D)quantum dots(QDs)and two-dimensional(2D)transition metal dichalcogenides(TMDs)materials are expected to attract great interest in optoelectronics due to the potential to generate new optical properties.Here,we report on the unique optical characteristics of a devices with mixed dimensional vertically stacked structures based on tungsten diselenide(WSe_(2))/CdSeS QDs monolayer/molybdenum disulfide(MoS_(2))(2D/0D/2D).Specifically,it exhibits an ambipolar photoresponse characteristic,with a negative photoresponse observed in the 400-600 nm wavelength range and a positive photoresponse appeared at 700 nm wavelength.It resulted in the high negative responsivity of up to 52.22 mA·W^(−1)under 400 nm,which is 163 times higher than that of the photodetector without CdSeS QDs.We also demonstrated the negative photoresponse,which could be due to increased carrier collision probability and non-radiative recombination.Device modeling and simulation reveal that Auger recombination among the types of non-radiative recombination is the main cause of negative photocurrent generation.Consequently,we discovered ambipolar photoresponse near a specific wavelength corresponding to the energy of quantum dots.Our study revealed interesting phenomenon in the mixed low-dimensional stacked structure and paved the way to exploit it for the development of innovative photodetection materials as well as for optoelectronic applications.

Fully tunable Fabry-Pérot cavity based on MEMS Sagnac loop reflector with ultra-low static power consumption

The Fabry-Pérot interferometer,a fundamental component in optoelectronic systems,offers interesting applications such as sensors,lasers,and filters.In this work,we show a tunable Fabry-Pérot cavity consisting of tunable Sagnac loop reflectors(SLRs)and phase shifters based on electrostatic microelectromechanical(MEMS)actuator.The fabrication process of the device is compatible with the standard wafer-level silicon photonics fabrication processes.This electrostatic actuation mechanism provides well-balanced,scalable pathways for efficient tuning methodologies.The extinction ratio of the continuously tunable SLRs’reflectivity is larger than 20 dB.Full 2πphase shifting is achieved,and response times of all the components are less than 25μs.Both actuators have extremely low static power,measuring under 20 fW and the energy needed for tuning is both below 20 pJ.