Photonic Crystal VCSEL Research Articles

Numerical investigation on self-heating effect in 1.3 µm quantum dot photonic crystal microstructure VCSELs

Numerical investigation on self-heating effect in 1.3 µm quantum dot photonic crystal microstructure VCSELs

Self-Heating Analysis of 1570 nm InGaAsP Buried Tunnel Junction Photonic Crystal VCSEL

In this paper, the lattice temperature in an InP-based 1570 nm InGaAsP buried tunnel junction photonic crystal vertical-cavity surface-emitting laser (BTJ-PhC VCSEL) was varied between 280 K until 370 K and its effects on the characteristics of the device was investigated. The temperature profiles of the BTJ-PhC VCSEL are obtained iteratively by considering their temperature-dependent material properties and the spatial distribution of all the significant heat sources. The thermal resistance used to model the electrical contacts causes about 8 K temperature increment above the ambient temperature (300 k) at a bias of 3 V and a 10.865 % increase in the threshold current is observed with temperature increment. This paper provides key results of the device characteristics upon lattice temperature, including the light power versus electrical voltage, the threshold current versus temperature, the wall-plug efficiency and the differential quantum efficiency versus temperature. Furthermore, various elements of heat sources within the active region were analyzed upon the increment of lattice temperature.

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.

Photonic Crystal VCSELs: Detailed Comparison of Experimental and Theoretical Spectral Characteristics

We present a detailed comparison of experimental and simulated optical spectra obtained from a 980-nm photonic-crystal (PhC) VCSEL. We demonstrate good qualitative agreement of the experimental spectra with the calculated emitted wavelengths for number of VCSEL structures with different PhC designs. We show the statistical analysis which reveals that strong confinement introduced by the photonic crystal contributes to the conformity between experiment and theory. For shallow etching of the photonic crystal holes, narrow optical aperture, and large diameter air-holes, we observe that diffraction and mode leakage through the PhC holes becomes the dominating phenomena, and then any fabrication imperfection may contribute to discrepancy between theory and experiment.

Photonic crystal VCSELs with narrow spectral width and high bandwidth operating at low current density

A photonic crystal vertical-cavity surface-emitting laser with a spectral width of 0.16 nm and a 3dB small signal modulation bandwidth of 16.2 GHz is demonstrated. Separation of optical and current apertures enables a narrow spectral width and an extremely low operating current density of ∼ 1 kA/cm2 simultaneously. It can potentially be used as a high-reliability laser source that enables error-free transmission over long multimode fibre links at high data rate.

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.

Analysis of single-mode condition and high-order modes discrimination in photonic crystal VCSEL

A new technique for analyzing the single-mode condition and mode discrimination of high-order modes in photonic crystal VCSEL is proposed and reported in this paper. The technique proposed is a semi-empirical approach that uses analytical analysis based on experimental data. For that purpose, single- and multimode photonic crystal VCSEL devices are fabricated and characterized for comparison of device performance. The mode width for first- and second-order mode of PhC VCSEL is computed for analyzing the mode behavior. In order to verify the findings, the fabricated single- and multimode devices are analyzed using finite difference frequency domain technique for the purpose of showing the loss as a function of mode order for the PhC VCSEL. The results show close agreement between the computed and experiment findings, justifying the use of the proposed semi-empirical technique for analyzing single-mode condition and of high-order modes discrimination in photonic crystal VCSEL.

Highly confined and continuous single-mode operation of self-align photonic crystal oxide VCSEL

In this letter, we report on single-mode operation of originally multi-mode oxide VCSEL by using etched photonic crystal air holes and unique trench structure. The device fabrication utilized conventional photolithography; with simplified lithography step of self-aligning the photonic crystal and trench structures to the laser aperture for efficient and vigorous device processing. The fabricated photonic crystal VCSEL with trench device exhibits a single-mode output power of 0.7 mW, threshold current of 3.5 mA, slope efficiency of 0.10 W/A, and continuous single-mode output spectra at wide operating current range. The results are compared with conventional multi-mode oxide VCSEL of similar device geometry. In addition, theoretical analysis is presented for developing further understanding of the photonic crystal VCSEL.

Loss Analysis of High Order Modes in Photonic Crystal Vertical-Cavity Surface-Emitting Lasers

A new technique for analyzing the loss of high order modes in photonic crystal VCSEL is reported. The technique proposed is a semi-empirical approach that uses comparison to experimental data. For that purpose, photonic crystal VCSEL devices of single mode and multi mode are fabricated and measured for device characteristics comparison. The fabricated devices are modeled using finite difference frequency domain technique for the purpose of investigating the photonic crystal guided modes and loss analysis. In order to verify the findings, full three dimensional analyses are performed based on the fabricated single mode and multi mode devices structures using common finite difference time domain technique. The results show close agreement between the computed and experiment findings, justifying the used of the proposed semi-empirical technique for analyzing the loss of high order modes in photonic crystal VCSEL. Results for guided modes and near- and far-field are also presented for the photonic crystal VCSEL.

Single transverse mode control of VCSEL by photonic crystal and trench patterning

Single transverse mode control is achieved for multimode GaAs-based VCSEL by utilizing photonic crystal design and etched trench structure. Theoretical analysis is initially performed for photonic crystal design with various lattice constants and air holes diameter. The fabricated photonic crystal VCSEL with etched trench structure exhibits single mode output power of 0.7 mW, threshold current of 3.5 mA, slope efficiency of 0.10 W/A, and continuous single mode output spectrum throughout a wide operating current range. Comparison of typical oxide VCSEL, trench oxide VCSEL, and photonic crystal oxide VCSEL employing trench structure is presented. By combining photonic crystal and trench structure, single transverse mode operation of photonic crystal VCSEL can be much more strictly controlled.

Thermal properties and wavelength analysis of telecom oriented photonic-crystal VCSELs

AbstractResults of the self-consistent comprehensive analysis of a room-temperature operation of InP-based 1300-nm AlInGaAs photonic-crystal (PhC) VCSELs are presented. In particular, an influence of PhC parameters on thermal effects within VCSEL volume and its emission wavelength are analysed. The PhC has been found to introduce a number of opposite effects including a possible light leakage through PhC holes. From one side, PhC holes make more difficult heat-flux extraction from VCSEL volume leading to higher temperature increases within it. But, from the other side, a properly manufactured PhC creates an efficient radial confinement mechanism for VCSEL radiation field. It enhances an interaction between the field and the active-region carriers leading to a decrease in both the VCSEL lasing threshold and temperature increases. Seemingly both effects may similarly affect VCSEL operation, but our analysis revealed, that thermal properties of the PhC VCSEL are mainly dependent on an efficient confinement of its radiation field within the active region impeding a mode leakage through PhC holes, whereas an importance of deterioration of heat-flux extraction from VCSEL volume is much less essential. The wavelength shift induced by a change of PhC parameters has been found not to exceed 4×10−3 µm.

Highly birefringent and dichroic photonic crystal VCSEL design

We analyse the possibility to stabilise the polarisation of light emitted by photonic crystal vertical-cavity surface-emitting lasers (PC-VCSELs). We consider two different photonic crystal configurations in a GaAs/AlGaAs VCSEL: with elliptical holes and with selectively enlarged holes and a small central hole. Very large birefringence (∼400GHz) and dichroism (∼7%) are demonstrated for the second PC-VCSEL design.

Numerical analysis of high Q-factor photonic-crystal VCSELs with plane-wave admittance method

The paper presents the application of a novel plane-wave admittance method (PWAM) to the three-dimensional and fully vectorial modeling of vertical-cavity surface-emitting lasers with incorporated photonic crystal. The basic mathematical details of the method are given and its convergence is verified for a sample structure. Then the simulations performed with PWAM are used to determine the optimal photonic crystal parameters for low-loss, high-Q-factor regime.