Photonic Crystal Vertical Cavity Surface Research Articles

Analysis and Characterization of Photon-Photon Resonance in Coupled Dual-Element Photonic Crystal Vertical Cavity Surface Emitting Laser Arrays

Analysis and Characterization of Photon-Photon Resonance in Coupled Dual-Element Photonic Crystal Vertical Cavity Surface Emitting Laser Arrays

Analysis of Coherence and Coupling in Vertical Cavity Surface Emitting Laser Arrays

The optical coupling between dual elements of photonic crystal vertical cavity surface emitting laser arrays is characterized. The optically coupled microcavity lasers have independent bias injection currents. Output power and beam analysis measurements are used to quantify the effects of optical coherence in nominally 850 nm emitting arrays. Modelling and experiment show how the optical coupling is influenced by photonic crystal lattice period and the independent current injection into the elements.

Low Divergence Coherently Coupled Vertical Cavity Surface Emitting Laser Ring Arrays

We report the theory and experimental verification of a method to reduce beam divergence from coherently-coupled ring arrays of photonic crystal vertical cavity surface emitting lasers (VCSELs). The photonic crystal etched into the top distributed Bragg reflector defines the optically coupled array elements, each of which has independent current injection and thus independent gain. Using a 2-dimensional complex waveguide model we simulate the supermodes of a 6-element ring array of VCSELs. The influence of the photonic crystal, free carrier loss, laser gain, and carrier-induced index suppression arising from the spatially defined gain regions are included in our analysis. Our simulations show the latter enables preferred anti-guided supermodes with reduced beam divergence. Optical characterization of the spectral and beam characteristics of 6-ring photonic crystal implanted VCSEL arrays shows that when the arrays are current-tuned to quasi-single mode operation, we find the beam divergence angle approaches 2° consistent with our simulations. This method of reduced beam divergence may have advantages for high-brightness applications.

Complex Waveguide Supermode Analysis of Coherently-Coupled Microcavity Laser Arrays

Coherently coupled microcavity lasers have desirable properties for emerging applications. We use 2-dimensional complex refractive index waveguide modeling of 2-element photonic crystal vertical cavity surface emitting laser arrays to analyze their supermodes. The complex modal effective indices are used in turn to calculate the complex coupling coefficient between the laser array elements. An analysis of the effects of array design parameters, such as photonic crystal period, fill-factor, or confinement, to engineer the coupling coefficient for the desired properties is given and example designs for 850 nm arrays are presented.

Simplified modeling of frequency behavior in photonic crystal vertical cavity surface emitting laser with tunnel injection quantum dot in active region

In this work, the characteristics of the photonic crystal tunneling injection quantum dot vertical cavity surface emitting lasers (PhC-TIQD-VCSEL) are studied through analyzing a modified modulation transfer function. The function is based on the rate equations describing the carrier dynamics at different energy levels of dot and injector well. Although the frequency modulation response component associated with carrier dynamics in wetting layer (WL) and at excited state (ES) levels of dots limits the total bandwidth in conventional QD-VCSEL, our study shows that it can be compensated for by electron tunneling from the injector well into the dot in TIQD structure. Carrier back tunneling time is one of the most important parameters, and by increment of that, the bias current dependence of the total bandwidth will be insignificant. It is proved that at high bias current, the limitation of the WL-ES level plays an important role in reducing the total bandwidth and results in rollovers on 3-dB bandwidth-I curves. In such a way, for smaller air hole diameter of photonic crystal, the effect of this reduction is stronger.

Single fundamental mode photonic crystal VCSEL with high power and low threshold current optimized by modal loss analysis**Project supported by the National Basic Research Program of China (Grant Nos. 2010CB934104, 2009CB320300, and 2011CBA00608) and the National Natural Foundation of China (Grant Nos. 61604007, 61378058, 61376049, 61575008, and 61574011).

The characteristics of the photonic crystal vertical cavity surface emitting lasers (PhC-VCSELs) were investigated by using the full vector finite-difference time-domain (FDTD) method through the transverse mode loss analysis. PhC-VCSELs with different photonic crystal structures were analyzed theoretically and experimentally. Through combining the dual mode confinement of oxide aperture and seven-point-defect photonic crystal structure, the PhC-VCSELs with low threshold current of 0.9 mA and maximum output power of 3.1 mW operating in single fundamental mode were demonstrated. Mode loss analysis method was proven as a reliable and useful way to analyze and optimize the PhC-VCSELs.

质子注入型光子晶体垂直腔面发射激光器制备

质子注入型光子晶体垂直腔面发射激光器制备

质子注入型光子晶体垂直腔面发射激光器制备

质子注入型光子晶体垂直腔面发射激光器制备

Multi-point defect single-fundamental-mode photonic crystal vertical cavity surface emitting laser

A seven-point-defect photonic crystal (PhC) vertical cavity surface emitting laser (VCSEL) operating with high single-fundamental-mode of 2.3mW and low threshold current of 1.2mA was demonstrated and its performance was analyzed. The single-fundamental-mode emission aperture (central defect area) was enlarged to achieve high output power. Furthermore, suitable refractive index step due to the photonic crystal structure was obtained to overcome the external index perturbations, which can be attributed to stable single-fundamental-mode operation even at saturation current. The transverse mode confinement characteristics by photonic crystal was analyzed based on the effective index model and showed good agreement with the experiment results.

Vertical cavity surface emitting laser transverse mode and polarization control by elliptical hole photonic crystal

The polarization of traditional photonic crystal (PC) vertical cavity surface emitting laser (VCSEL) is uncontrollable, resulting in the bit error increasing easily. Elliptical hole photonic crystal can control the transverse mode and polarization of VCSEL efficiently. We analyze the far field divergence angle, and birefringence of elliptical hole PC VCSEL. When the ratio of minor axis to major axis b/a = 0.7, the PC VCSEL can obtain single mode and polarization. According to the simulation results, we fabricate the device successfully. The output power is 1.7 mW, the far field divergence angle is less than 10°, and the side mode suppression ratio is over 30 dB. The output power in the Y direction is 20 times that in the X direction.

Various Elements of Heat Sources within an Optimized Photonic Crystal Vertical Cavity Surface Emitting Laser: Influence of Hole Etching Depth

Various Elements of Heat Sources within an Optimized Photonic Crystal Vertical Cavity Surface Emitting Laser: Influence of Hole Etching Depth

Single Mode Photonic Crystal Vertical Cavity Surface Emitting Lasers

We review the design, fabrication, and performance of photonic crystal vertical cavity surface emitting lasers (VCSELs). Using a periodic pattern of etched holes in the top facet of the VCSEL, the optical cavity can be designed to support the fundamental mode only. The electrical confinement is independently defined by proton implantation or oxide confinement. By control of the refractive index and loss created by the photonic crystal, operation in the Gaussian mode can be insured, independent of the lasing wavelength.

Hydrogen Detection Using a Functionalized Photonic Crystal Vertical Cavity Laser

A thin layer of palladium (Pd) was deposited on the surface of an etched air hole photonic crystal (PhC) vertical cavity surface emitting laser (VCSEL) to form a hydrogen gas (H2) sensor. H2 reacts with Pd, forming PdHx, which induces a shift in the complex refractive index. With Pd on its surface, the reflectivity of the top distributed Bragg reflector depends on the H2 concentration. We present device operation theory and experimental results showing a 60% output power increase and a 52 pm redshift of the lasing wavelength at 4% H2. Since the PhC VCSEL laser is single mode and the wavelength shift is comparable to the laser linewidth, the sensor can provide an accurate quantification of the H2 concentration over the range of 0-4% H2.

Study on influence of oxide aperture shape on modal characteristics of VCSELs

The effects of oxide aperture shape whose size is small, on the mode characteristics of external cavity oxide-confined photonic crystal vertical cavity surface emitting laser (VCSEL) is studied extensively based on the finite-difference time-domain algorithm. A new three-dimensional model of optical field in photonic crystal VCSEL is built and the influence of the variation in aperture shape on the characteristics of far-field and spectrum is pointed out. It is found that the modal characteristics of PhC-VCSEL are influenced by the shape of oxide aperture, the influence on spectrum feature is more apparent. It can be explained from the distribution of modal field by the fact that the symmetrical characteristic of prismatic oxide aperture is not identical to that of high-order mode. But the influence is less apparent while the depth of photonic crystal hole is deeper. The reason for this matter is illustrated. The results can be used to guide the fabrication of external cavity oxide-confined photonic crystal VCSELs.

High Q vertical surface emitting photonic crystal surface-mode cavities with periodic perturbation

We introduce a periodical perturbation to realize photonic crystal vertical cavity surface emitting laser cavities based on surface modes (PCSM-VCSEL) and to enhance their quality factor. Different from the early reported direct periodical modulation to the cavity surface, a periodical perturbation under the surface can also result in the vertical emission due to the beaming effect. It is more important that this perturbation causes less energy diffraction loss or light output because the perturbation is imposed on not the center but the tail of the field of surface modes. Therefore, this modulation method greatly improves the quality factor of such PCSM-VCSEL cavities, which is favorable to their realization in practice. The numerical results demonstrate their characteristics and good performances in the application as light sources.

A Single-Fundamental-Mode Photonic Crystal Vertical Cavity Surface Emitting Laser with Seven-point Defect

A single-fundamental-mode photonic crystal (PhC) vertical cavity surface emitting laser (VCSEL) with seven-point defect was fabricated by etching two-dimensional PhC on surface of the VCSEL's top distributed Bragg-reflector (DBR). The PhC was fabricated using electron beam lithography (EBL) and inductive coupled plasma reactive ion etching (ICP-RIE). The single-fundamental-mode performances were investigated and demonstrated. The device with output power 0.7mW under continuous-wave (CW) operate, half maximum of the lasing spectrum less than 0.06nm, far field divergence angle less than 10° and side mode suppression ratio over 35dB was obtained. The characteristics of the PhC VCSEL operating at pulse condition are compared with VCSEL with the similar aperture size, we found that the output power of PhC VCSEL increased more than conventional VCSEL with the impulse duty factor decreased, corresponding to 100% and 32%, respectively.

Full 3D FDTD analysis of Electromagnetic Field in Photonic Crystal VCSEL

The effect of etch damage to the mode characteristics of photonic crystal vertical cavity surface emitting lasers was simulated in this paper. The devices simulated in this paper are 850-nm GaAs-based VCSELs with photonic crystal. And the devices were simulated by using finite difference time domain (FDTD) method. Limited to the computer resource, the top DBR was simulated only, and the traverse size was smaller than the real size. In order to highlight the impact of the etch damage, several kinds of light sources and photonic crystal structures were simulated separately, and each situation is calculated in the condition of ideal photonic crystal and photonic crystal with etch damage respectively. All parameters of device and light feature are referred to the real condition.

A Single-Fundamental-Mode Photonic Crystal Vertical Cavity Surface Emitting Laser

Single-fundamental-mode photonic crystal (PhC) vertical cavity surface emitting lasers (VCSEL) are produced and their single-fundamental-mode performances are investigated and demonstrated. A two-dimensional PhC with single-point-defect structure is fabricated using UV photolithography and inductive coupled plasma reactive ion etching on the surface of the VCSEL's top distributed Bragg-reflector. The PhC VCSEL maintains single-fundamental-mode operating with output power 1.7 mW and threshold current 2.5mA. The full width half maximum of the lasing spectrum is less than 0.1 nm, the far field divergence angle is less than 10° and the side mode suppression ratio is over 35 dB. The device characteristics are analyzed based on the effective index model of the photonic crystal fiber. The experimental results agree well with the theoretical expectation.

Study on current spreading of photonic crystal vertical cavity surface emitting lasers

The distribution of injected current in the active region of external cavity oxide-confined photonic crystal vertical cavity surface emitting lasers is studied extensively. An advanced three-dimensional model of current distribution is used to analyse the effects of photonic crystal structures on current density distribution and series resistance of the device. It is found that the deeper the photonic crystal holes are, the worse the circular symmetry of the current density distribution is and the higher the series resistance is,especially when the ethching depths of holes are larger than 2 μm. Different patterns of photonic crystal structures have a great imfluence on current density distribution and circular symmetry. The results are beneficial to the research and the design of external cavity oxide-confined photonic crystal vertical cavity surface emitting lasers.

A novel photonic crystal vertical cavity surface emitting laser based on coherent coupling

We demonstrate a novel oxide confined GaAs-based photonic crystal vertical cavity surface emitting laser (PC-VCSEL) operating at a wavelength of 850 nm based on coherent coupling. A ring-shaped light-emitting aperture is added to the conventional PC-VCSEL, and coherent coupling is achieved between the central defect aperture and the ring-shaped light-emitting aperture. Measurements show that under the continuous-wave (CW) injected current of 20 mA, a high power of 2 mW is obtained, and the side mode suppression ratio (SMSR) is larger than 20 dB. The average divergence angle is 4.2° at the current level of 20 mA. Compared with the results ever reported, the divergence angle is reduced.