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 2.5 mA. The full width half maximum of the lasing spectrum is less than 0.1 nm, the far field divergence angle is less than 10 degrees 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.

Blue-green optically pumped GaN-based vertical cavity surface emitting laser

Blue-green GaN-based vertical cavity surface emitting lasers (VCSELs) were fabricated with two dielectric Ta2O5/SiO2 distributed Bragg reflectors. Lasing action was observed at a wavelength of 498.8 nm at room temperature under optical pumping. Threshold energy density and emission linewidth were 189 mJ/cm(2) and 0.15 nm, respectively. The result demonstrates that blue-green VCSELs can be realised using III-nitride semiconductors.

Reduced divergence angle of photonic crystal vertical-cavity surface-emitting laser

The reduced divergence angle of the photonic crystal vertical-cavity surface-emitting laser (PC-VCSEL) was investigated in both theory and experiment. The photonic crystal waveguide possessed the weakly guiding waveguide characteristic, which accounted for the reduction of the divergence angle. The three-dimensional finite-difference time-domain method was used to simulate the designed PC-VCSEL, and a calculated divergence angle of 5.2 degrees was obtained. The measured divergence angles of our fabricated PC-VCSEL were between 5.1 degrees and 5.5 degrees over the entire drive current range, consistent with the numerical results. This is the lowest divergence angle of the fabricated PC-VCSEL ever reported.

Blue-violet Lasing of Optically Pumped GaN-Based Vertical Cavity Surface-Emitting Laser With Dielectric Distributed Bragg Reflectors

Optically pumped GaN-based vertical cavity surface-emitting laser (VCSEL) with two Ta2O5/SiO2 dielectric distributed Bragg reflectors (DBRs) was fabricated via a simplifled procedure direct deposition of the top DBR onto the GaN surface exposed after substrate removal and no use of etching and polishing processes. Blue-violet lasing action was observed at a wavelength of 397.3 ran under optical pumping at room temperature with a threshold pumping energy density of about 71.5 mJ/cm(2). The laser action was further confirmed by a narrow emission linewidth of 0.13 nm and a degree of polarization of about 65%. The result suggests that practical blue-violet GaN-bsaed VCSEL can be realized by optimizing the laser lift-off technique for substrate removal.

Single mode vertical-cavity surface emitting laser with surface plasmon nanostructure

The vertical-cavity surface-emitting laser(VCSEL) has proved to be a low cost light source with attractive properties such as surface emission, circular and low divergence output beam, and simple integration in two-dimensional array. Many new applications such as in spectroscopy, optical storage, short distance fiber optic interconnects, and in longer distance communication, are continuously arising. Many of these applications require stable and single-mode high output power. Several methods that affect the transverse guiding and/or introduce mode selective loss or gain have been developed. In this study, a method for improving the single mode output power by using metal surface plasmons nanostructure is proposed. Theoretical calculation shows that the outpout power is improved about 50% compared to the result of standard VCSELs.

Surface plasmon modulated nano-aperture vertical-cavity surface-emitting laser

Surface plasmon modulated nano-aperture vertical-cavity surface-emitting lasers were fabricated from common 850 nm VCSELs. When the diameter of the aperture was 200 nm, and the period of grating was 400 nm, the maximum far-field output power reached 0.3mW at a driving current of 15 mA. The fabrication process was described and the beaming properties were studied via experimentally and theoretically.

Photonic crystal vertical-cavity surface-emitting laser based on GaAs material

A photonic crystal vertical-cavity-surface-emitting laser ( PC-VCSEL) with a wavelength of about 850 nm was realized. The direct-current electrically-driven PC-VCSELs with a minimum threshold current of 2 mA and a maximum threshold current of 13.5 mA were obtained. We fabricated a series of PC-VCSEL chips whose lattice constants are in the range from 0.5 to 3 mu m with different filling factors, and found that the laser characterization depends on the lattice constant, the filling factor, the size of cavity, etc.

Surface plasmon modulated nano-aperture vertical-cavity surface-emitting laser

We have fabricated surface plasmon modulated nano-aperture vertical-cavity surface-emitting lasers (VCSELs) from common 850 nm VCSELs using focus ion beam etching with Ga+ ion source. The far-field output power is about 0.3 mW at a driving current of 15 mA with a sub-wavelength aperture surrounded by concentric periodic grooves. The enhancement of transmission intensity can be explained by diffraction and enhanced fields associated with surface plasmon. This structure also exhibits beaming properties.

Stability improvement of selective oxidation during the fabrication of InGaAs/GaAs vertical cavity surface emitting laser

The effects of the carrier gas flow and water temperature on the oxidation rate for different reaction temperatures were investigated. The optimum conditions for stable oxidation were obtained. Two mechanisms of the oxidation process are revealed. One is the flow-controlling process, which is unstable. The other is the temperature-controlling process, which is stable. The stable region decreases for higher reaction temperatures. The simulation results for the stable oxidation region are also given. With optimum oxidation conditions, the stability and precision of the oxidation can be dramatically improved.

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 degrees at the current level of 20 mA. Compared with the results ever reported, the divergence angle is reduced.

Single-mode holey vertical-cavity surface-emitting laser with ultra-narrow beam divergence

We demonstrated oxide-confined 850-nm vertical-cavity surface-emitting lasers (VCSELs) with a two-dimensional petal-shaped holey structure composed of several annular-sector-shaped holes. Four types of devices with different hole numbers were designed and fabricated. The measured results showed that the larger hole number was beneficial to purifying the lasing mode, and realizing the single-mode operation. The side mode suppression ratio (SMSR) exceeded 30 dB throughout the entire drive current. Mode selective loss mechanism was used to explain the single-mode characteristic. The single-mode devices possessed good beam profiles, and the lowest divergence angle was as narrow as 3.2 degrees (full width at half maximum), attributed to the graded index profile and the shallow etching in the top distributed Bragg reflector (DBR).

Phase-locked ring-defect photonic crystal vertical-cavity surface-emitting laser

Phase-locked oxide-confined ring-defect photonic crystal vertical-cavity surface-emitting laser is presented. The coupled-mode theory is employed to illustrate the two supermodes of the device, in-phase and out-of-phase supermode. Experimental results verify the two supermodes by the characteristics of the spectra and the far field patterns. At the lower current, only the out-of-phase supermode is excited, whereas under the higher current, the in-phase supermode also appears at the shorter wavelength range. In addition, the measured spectral separation between the two supermodes agrees well with the theoretical result.

EFFECTIVE CAVITY LENGTH IN VERTICAL-CAVITY SURFACE-EMITTING LASER

Effective cavity length method is introduced to vertical cavity surface emitting laser for characterizing some properties, including reflectivity FWHM, mode wavelength and threshold gain. Some experiment results are demonstrated, showing the agreement of theoretical analysis with experiment.

Visible vertical cavity surface emitting laser

We have designed and fabricated the visible vertical-cavity surface-emitting lasers (VCSEL's) by using metalorganic vapor phase epitaxy (MOVPE). We use the 8 lambda optical cavities with 3 quantum wells in AlGaInP/AlGaAs red VCSEL's to reduce the drift leakage current and enhance the model gain in AlGaInP active region. The structure has a p-type stack with 36 DBR pairs on the top and an n-type with 55-1/2 pairs on the bottom. Using micro-area reflectance spectrum, we try to get a better concordance between the center wavelength of DBR and the emitting wavelength of the active region. We used a component graded layer of 0.05 lambda thick (x = 0.5 similar to 0.9) at the p-type DBR AlGaAs/AlAs interface to reduce the resistance of p-type DBR. We use selective oxidation to define the current injection path. Because the oxidation rate of a thick layer is faster than a thinner one, we grown a thick AlAs layer close to the active region. In this way, we got a smaller active region for efficient confinement of injected carriers (the aperture area is 3 x 3 mu m) to reduce the threshold and, at the same time, a bigger conductive area in the DBR layers to reduce the resistance. We employ Zn doping on the p-side of the junction to improve hole injection and control the Zn dopant diffusion to get proper p-i-n junction. At room temperature, pulse operation of the laser has been achieved with the low threshold current of 0.8mA; the wavelength is about 670nm.

Stability improvement of selective oxidation during the fabrication of InGaAs/GaAs vertical cavity surface emitting laser

The effects of the carrier gas flow and water temperature on the oxidation rate for different reaction temperatures were investigated. The optimum conditions for stable oxidation were obtained. Two mechanisms of the oxidation process are revealed. One is the flow-controlling process, which is unstable. The other is the temperature-controlling process, which is stable. The stable region decreases for higher reaction temperatures. The simulation results for the stable oxidation region are also given. With optimum oxidation conditions, the stability and precision of the oxidation can be dramatically improved.