GeSn alloys hold the promise for the development of on-chip, scalable, industry-compatible light sources. Here, we introduce a novel strain engineering approach to create tensile-strained GeSn microlasers. Through a unique lithographic design, the initially harmful compressive strain intrinsic to the GeSn layers is converted to the beneficial tensile strain and amplified on the GeSn microbridges. By tuning the design parameters of the microbridges, multiple lasers with different tensile strains were achieved on a single chip. We anticipate that increasing the tensile strain will lead to a shift in the lasing wavelength and an improvement in the laser threshold. This work presents a straightforward and cost-effective solution for developing diverse on-chip laser arrays, enabling applications such as on-chip wavelength division multiplexing.
We present a strain engineering platform that allows the dynamic tuning of the emission wavelength of a monolayer WSe2. A large and localized strain was induced in monolayer 2D materials by patterning a photoresist layer with internal stress into two elliptical shapes with a finite gap in between, which is referred to as a dimer in this work. By applying laser annealing on the dimer stressor while monitoring the exciton emission, we demonstrate the capability to dynamically tune the emission wavelength of the bright exciton in the monolayer WSe2.
The photonics-based approach has recently become a strong candidate for realising a large-scale, practical quantum processor. Particularly in recent years, two-dimensional (2D) materials have become a strong candidate for developing an ideal integrated light source owing to their several unique advantages such as convenient on-chip integration. In this work, we study the effect of strain on the emission wavelength and carrier lifetime. We first show that the geometry of stressors can adjust the amount of strain and emission wavelength. Using this strain engineering technique, we demonstrate that the emission wavelength can be significantly shifted by ~10 nm while the carrier lifetime can also be engineered by ~30 %.
Despite its superior physical properties, graphene’s optical properties still possess crucial drawbacks for both classical and quantum photonics applications. For example, graphene’s gapless band structure prohibits efficient light emission, while its centrosymmetric nature renders it impossible to obtain strong second-order nonlinearity. In this work, we discuss our latest results on strained graphene that provides a new pathway towards solving the two key above-mentioned problems.
Pseudo-magnetic field in strained graphene has emerged as a promising route to allow observing intriguing physical phenomena that would be inaccessible with laboratory superconducting magnets. However, experimental observation of the impact of pseudo-magnetic field on optical and electrical properties of graphene has remained unknown. Here, using time-resolved infrared pump-probe spectroscopy, we provide unambiguous evidence of slow carrier dynamics enabled by a giant pseudo-magnetic field (~100 T) in periodically strained graphene. Our finding presents unforeseen opportunities towards harnessing the new physics of graphene in previously unachievable high magnetic field regimes.
GeSn alloys have emerged as a promising material for realizing CMOS-compatible light sources. GeSn lasers demonstrated to date have large device footprints and active areas, which limit the realization of densely integrated lasers operating at low power consumption. Thanks to their intrinsically small device form factors, 1D photonic crystal lasers may offer opportunities to overcome such limitations of large GeSn lasers. Here, we present a 1D photonic crystal nanobeam laser with a very small device footprint (~7 μm2) and a compact active area (~1.2 μm2) on a GeSn-on-insulator substrate.
Combining Sn alloying and tensile strain to Ge has emerged as the most promising engineering approach to create an efficient Si-compatible lasing medium. The residual compressive strain in GeSn has thus far made the simple geometrical strain amplification technique unsuitable for achieving tensile strained GeSn. Herein, by utilizing two unique techniques, we report the introduction of a uniaxial tensile strain directly into GeSn micro/nanostructures. By converting GeSn from indirect to direct bandgap material via tensile strain, we achieve a 10-fold increase in the light emission intensity.
In the quest for practical group IV lasers, researchers have proposed a few ideas such as strain engineering of Ge and alloying of Sn into Ge. Both approaches fundamentally alter bandstructure such that Ge can become a direct bandgap material. Recently, relaxation of limiting compressive strain and addition of mechanical tensile strain have been employed to improve the lasing performance. However, such strain engineering has thus far been possible only in suspended device configurations, which significantly limit heat dissipation and hinder the device performance. We herein demonstrate GeSn microdisk lasers fully released on Si that relax the limiting compressive strain and achieve excellent thermal conduction.
The potential for establishing energy gaps by pseudo-magnetic fields in strain-engineered graphene has sparked much interest recently. However, the limited sizes of induced pseudo-magnetic fields and the complicated platforms for straining graphene have thus far prevented researchers from harnessing the unique pseudo-magnetic fields in optoelectronic devices. In this work, we present an experimental demonstration of triaxially strained suspended graphene structures capable of obtaining quasi-uniform pseudo-magnetic fields over a large scale. The novel metal electrode design functions as both stressors and current injectors. We also propose a hybrid laser structure employing a 2D photonic crystal and triaxially strained graphene as an optical cavity and gain medium, respectively.
Integration of photonic devices with CMOS circuits has recently generated much interest for numerous applications ranging from Internet networks to sensor technology. For example, integrated optical interconnects have emerged as a strong contender to replace bandwidth-hungry and energy-guzzling electrical interconnects in data centers and inside microprocessors. However, the lack of group IV semiconductor materials suitable for light emission has thus far prevented the realization of such important photonic-integrated circuits. In this paper, we will present our research works on strain-engineered group IV light sources on silicon that will help enable photonic-integrated circuits.
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