The SiO ₂ /SiN _x dielectric film stacks deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD) are employed on the top of the oxide-confined vertical-cavity surface-emitting lasers (VCSELs). The reflecting mirror characteristics of the dielectric films are measured with varying numbers of pairs from 4 to 12. The prepared devices have low threshold current of 0.3 mA, single-mode peak power of 1.4 mW at room temperature. The thermal resistance of the device depending on ambient temperature is estimated according to the relationship of wavelength shift and dissipated power, allowing us to extract the actual temperature in active region and the temperature dependence of the output characteristics of the VCSEL. The beam property of the device is characterized by the far field pattern (FFP). Depending on the drive current, the average divergence angles of the output beam estimated from the full-width-half-maximum (FWHM) of the FFP varies between 20.4° and 21.2°. Furthermore, polarization-controlled single mode emission is achieved by introducing a built-in grating into the VCSEL with orthogonal polarization suppression ratio (OPSR) around 19 dB.

Multiple Fano resonances (FRs) can be produced by destroying the symmetry of structure or adding additional nanoparticles without changing the spatial symmetry, which has been proved in noble metal structures. However, due to the disadvantages of low modulation depth, large damping rate, and broadband spectral responses, many resonance applications are limited. In this research paper, we propose a graphene plasmonic metamolecule (PMM) by adding an additional 12 nanodiscs around a graphene heptamer, where two Fano resonance modes with different wavelengths are observed in the extinction spectrum. The competition between the two FRs as well as the modulation depth of each FR is investigated by varying the materials and the geometrical parameters of the nanostructure. A simple trimer model, which emulates the radical distribution of the PMM, is employed to understand the electromagnetic field behaviors during the variation of the parameters. Our proposed graphene nanostructures might find significant applications in the fields of single molecule detection, chemical or biochemical sensing, and nanoantenna.

We demonstrate a polarization-stable and single-mode grating-coupled surface-emitting laser (GCSEL) with high side-mode suppression ratio (SMSR) of ∼40 dB and orthogonal polarization suppression ratio (OPSR) of ∼25 dB around 795 nm. The fabricated devices have low threshold current of ∼4.8 mA and low electrical resistance of 53 Ω at 25 °C. Meanwhile, a low thermal resistance of ∼1 K/mW is achieved, which is comparable with that of the record of ever reported for vertical-cavity surface-emitting lasers (VCSELs). The far-field divergence angle of surface-emitting beam is ∼14.5°x14.7° at an injection current of 12 mA indicating a relatively good beam quality. Our results open what we believe is a new way to produce polarization-stable single-mode surface-emitting lasers with simple fabrication process. While the GCSEL is specifically designed for quantum sensing applications such as atomic clocks, magnetometers, and gyroscope, its performance in terms of low-power consumption, low thermal resistance, good beam qualities, and wafer-level testing are of particular interest for a wide range of applications.

We fabricate 850-nm vertical-cavity surface-emitting lasers (VCSELs) with oxide-aperture diameters of 5, 7, 9 and $11~\mu $ m and study the effect of oxide-aperture size on the threshold current, output power, differential quantum efficiency and wall-plug efficiency of the devices. We characterize the small-signal modulation bandwidth ( ${f} _{3dB}$ ) of the devices and explore the impact of oxide-aperture size and bias current on the modulation bandwidth. We analyze the relationship between electrical power and the ${f} _{3dB}$ of the VCSELs with different aperture diameters. The fabricated 850-nm VCSEL with the oxide-aperture diameter of $7~\mu $ m at room temperature shows a maximum ${f} _{3dB}$ of nearly 20 GHz and an output power of 9.09 mW. When the oxide-aperture increases to $11~\mu $ m, the ${f} _{3dB}$ remains above 17 GHz and the optical output power exceeds 14 mW.

We propose the monolayer graphene plasmonic waveguide (MGPW), which is composed of graphene core sandwiched by two graphene metamaterial (GMM) claddings and investigate the properties of plasmonic modes propagating in the waveguide. The effective refraction index of the GMMs claddings takes negative (or positive) at the vicinity of the Dirac-like point in the band structure. We show that when the effective refraction index of the GMMs is positive, the plasmons travel forward in the MGPW with a positive group velocity (vg > 0, vp > 0). In contrast—for the negative refraction index GMM claddings—a negative group velocity of the fundamental mode (vg < 0, vp > 0) appears in the proposed waveguide structure when the core is sufficiently narrow. A forbidden band appears between the negative and positive group velocity regions, which is enhanced gradually as the width of the core increases. On the other hand, one can overcome this limitation and even make the forbidden band disappear by increasing the chemical potential difference between the nanodisks and the ambient graphene of the GMM claddings. The proposed structure offers a novel scheme of on-chip electromagnetic field and may find significant applications in the future high density plasmonic integrated circuit technique.

795 nm oxide-confined distributed feedback (DFB) lasers have been developed. The oxide-confined structure is used to realize lateral optical and current confinement, and the first order surface gratings offer the frequency selectivity for single longitudinal mode operation. The fabricated 200-um-long devices exhibited a low-threshold current of ∼4.8 mA, a 3-dB modulation bandwidth of ∼5.8 GHz and maintained stable single mode operation around 795 nm with side mode suppression ratio (SMSR) as high as ∼40 dB. The simple and compact laser structure greatly reduces the difficulty of device design and fabrication compared with traditional DFB lasers. The characteristics of the laser, including low-threshold current, single mode stability and potentially narrow spectral linewidth, make it a suitable candidate for applications in absorption spectroscopy of the rubidium D1 line, chip-scale atomic clocks, magnetometers, and gyroscopes