Transverse Mode Vertical-cavity Surface-emitting Lasers Research Articles

Low Threshold Current and Polarization-Stabilized 795 nm Vertical-Cavity Surface-Emitting Lasers

Low threshold current and polarization-stabilized 795 nm vertical-cavity surface-emitting lasers (VCSELs) are fabricated by integrating a surface grating of high polarization selectivity and high reflectivity. The rigorous coupled-wave analysis method is used to design the surface grating. For the devices with a grating period of 500 nm, a grating depth of ~150 nm, and a diameter of the surface grating region of 5 μm, a threshold current of 0.4 mA and an orthogonal polarization suppression ratio (OPSR) of 19.56 dB are obtained. The emission wavelength of 795 nm of a single transverse mode VCSEL is achieved at a temperature of 85 °C under an injection current of 0.9 mA. In addition, experiments demonstrate that the threshold and output power also depended on the size of the grating region.

Tailored Transverse Mode Vertical-Cavity Surface-Emitting Laser: Hollow Laser Beam Emission through Circle Aperture

Vertical-cavity surface-emitting lasers that can be controlled to emit hollow laser beam in certain LP21 mode are proposed and fabricated. A circular inverted surface relief with precisely designed diameter and thickness is introduced through theoretical simulation. The fabricated device shows a stable single LP21 mode operation with excellent robustness of mode and power to temperature. Preliminary analysis attribute the excellent performance of the device to the inverted surface relief, leading to hollow near-field spot distribution.

Attractor hopping between polarization dynamical states in a vertical-cavity surface-emitting laser subject to parallel optical injection.

We present experimental and theoretical results of noise-induced attractor hopping between dynamical states found in a single transverse mode vertical-cavity surface-emitting laser (VCSEL) subject to parallel optical injection. These transitions involve dynamical states with different polarizations of the light emitted by the VCSEL. We report an experimental map identifying, in the injected power-frequency detuning plane, regions where attractor hopping between two, or even three, different states occur. The transition between these behaviors is characterized by using residence time distributions. We find multistability regions that are characterized by heavy-tailed residence time distributions. These distributions are characterized by a -1.83±0.17 power law. Between these regions we find coherence enhancement of noise-induced attractor hopping in which transitions between states occur regularly. Simulation results show that frequency detuning variations and spontaneous emission noise play a role in causing switching between attractors. We also find attractor hopping between chaotic states with different polarization properties. In this case, simulation results show that spontaneous emission noise inherent to the VCSEL is enough to induce this hopping.

Design Considerations for Single-Mode Vertical-Cavity Surface-Emitting Lasers With Impurity-Induced Intermixing

We report on the modeling of 850-nm (Al,Ga)As/GaAs vertical cavity surface-emitting lasers (VCSELs), where the electrical and optical confinement is realized by impurity-induced intermixing. The 3-D simulations of electromagnetic fields are performed by the finite-element method using full vector Maxwell’s equations. An example of a transverse junction VCSEL with Zn-induced intermixing of the areas surrounding the quantum well region is compared with the case of a VCSEL, where the optical modes are confined by selective oxidation of the Al-rich GaAlAs aperture layers. We show that Zn-induced intermixing results in a high efficiency of the leakage of the VCSEL aperture-confined modes into the surrounding intermixed area. Furthermore, there is a strong mode selectivity through the leakage loss between the fundamental and excited transverse modes of the optical cavity. This enables potential realization of a single transverse mode VCSEL at the aperture diameters of 10 $\mu \text{m}$ or above and consequently the realization of high-power single-mode VCSELs. Optimum mode selectivity is realized once the impurity intermixing profile proceeds down to the depth of about 2.6 $\mu \text{m}$ into the bottom distributed Bragg reflector below the quantum well region. Leakage of the optical modes into the intermixed area is accompanied by the evolution of narrow tilted lobes in the far-field emission spectra (at $\sim 60^{\circ }$ tilt angles for the design considered). This effect is similar to the one previously observed in oxide-confined leaky VCSELs and originates from the laterally propagating optical modes outside the non-intermixed aperture region. Where necessary, by applying such phenomenon, a phase-coupled array can be configured. We believe that such single-mode VCSELs may become extremely important in 3-D sensing, printing, and laser illumination. Furthermore, LIDARs with an option of beam steering without moving parts can be realized in 2-D phase-coupled arrays.

Polarization-resolved characterization of long-wavelength vertical-cavity surface-emitting laser parameters

A measurement of the parameters characterizing polarization behavior of a 1550 nm single transverse mode vertical-cavity surface-emitting laser (VCSEL) is presented from the analysis of CW high-resolution optical spectra. Current-induced polarization switching (PS) is observed in our device. A minimum in the absolute value of the effective dichroism is observed at the PS point. The value of the effective birefringence has a discontinuity at the current at which PS is observed. Birefringence oscillations with the bias current are also observed. PS characteristics are used for the extraction of the parameters describing the polarization behavior of the VCSEL. Obtained values of the spontaneous emission fraction and spin-flip rate are larger than those typically used in theoretical modeling of these devices.

Optical system design of a portable coherent population trapping (CPT) atom clock

We present the mechanism of coherent population trapping (CPT) atom clock. The optical system is designed for a portable CPT atom clock. In this system, single transverse mode vertical-cavity surface-emitting laser is used as a miniature pump laser. The driven circuit is designed based on a field-programmable gate array full digital control system and special-purpose chip MAX1968. The experimental results show that the optical system can provide circularly polarized light, and has small volume and low power consumption. These indi-cate that the optical system is a promising candidate for a portable CPT atom clock engineering prototype.

Polarization control of 0.85μm vertical-cavity surface-emitting lasers integrated with gold nanorod arrays

In this letter, the authors unambiguously demonstrate the polarization control of 0.85μm single transverse mode vertical-cavity surface-emitting lasers (VCSELs) using plasmonic nanorod arrays fabricated on the top surface of VCSELs. The strong direction dependent scattering of light from anisotropic gold nanorods enables stable polarization operations of VCSELs with suppressing the absorption in gold layer and leads to high differential quantum efficiencies. These nanorod arrays integrated VCSELs show negligible penalties in laser performances having the maximum output power of nearly 1mW with the side mode suppression ratio of 45dB and the orthogonal polarization suppression ratio of 21dB.

850 nm vertical-cavity laser pigtailed to standard singlemode fibre for radio over fibre transmission

An 850 nm single transverse mode vertical-cavity surface-emitting laser (VCSEL) pigtailed to a standard 1300 nm-optimised 9/125 µm singlemode fibre (SMF) is presented as a low-cost light source for radio over fibre transmission. The spurious-free dynamic range of a link using such a VCSEL pigtail is found to be above 90 dBHz2/3 up to 2 km of standard 9/125 µm SMF, thus fulfilling the requirements of mobile communication systems.

Single high-order transverse mode surface-emitting laser with controlled far-field pattern

Single transverse mode vertical-cavity surface-emitting lasers (VCSELs) with high output power are important for high-speed data links, optical recording, laser processing, and so on. We demonstrate a single high-order transverse mode VCSEL with narrow trenches formed on its top surface by using a focused ion beam. The formation of four straight cross trenches resulted in the selection of a stable LP/sub 41/ mode oscillation. A large far-field angle of the LP/sub 41/ mode, which causes a low coupling efficiency even with a multimode fiber, was drastically reduced by loading a phase shift layer. A single-lobe far-field pattern with low scattering loss was realized by loading a spatial phase shift of SiO/sub 2/. We evaluated a coupling efficiency with a single-mode fiber including its alignment tolerance. The controlled far-field pattern enables lens-free direct coupling with a single-mode fiber even for large active-area VCSELs.

Continuous wave single transverse mode vertical-cavity surface-emitting lasers fabricated by helium implantation and zinc diffusion

A single transverse mode vertical-cavity surface emitting laser with moderate power has been fabricated using helium implantation and zinc diffusion. Devices with a 4 μm diameter active region exhibited a fundamental transverse mode (TEM00) operation with a maximum continuous wave output power of 1.5 mW and a quantum efficiency as high as 70%.