Diameter Vertical-cavity Surface-emitting Lasers Research Articles

Relative intensity noise of temperature-stable, energy-efficient 980 nm VCSELs

The relative intensity noise (RIN) of temperature-stable, energy-efficient oxide confined vertical-cavity surface-emitting lasers (VCSELs) have been investigated. Low energy consumption data transmission is achieved by using small oxide-aperture diameter VCSELs biased at small currents. We demonstrate that energy efficiency is not in conflict with our VCSELs’ RIN characteristics. The experimental results indicate that small oxide-aperture diameter VCSELs, which are most suitable for energy-efficient, temperature-stable operation, exhibit lower laser RIN due to less mode competition inside the smaller optical cavity volume. Our energy-efficient VCSELs fulfill the RIN requirements of the 32G Fibre Channel standard.

20-Gb/s Modulation of Silicon-Integrated Short-Wavelength Hybrid-Cavity VCSELs

We investigate the dynamics of silicon-integrated 850-nm-wavelength hybrid-cavity vertical-cavity surface-emitting lasers (VCSELs). The VCSELs consist of a GaAs-based half-VCSEL attached to a dielectric distributed Bragg reflector on a silicon substrate using ultra-thin divinylsiloxane-bis-benzocyclobutene adhesive bonding. A 5- $\mu \text{m}$ oxide aperture diameter VCSEL, with a small signal modulation bandwidth of 11 GHz, supports data transmission at bit rates up to 20 Gb/s. The modulation bandwidth and the large signal modulation characteristics are found to be impaired by the high thermal impedance.

Silicon-integrated short-wavelength hybrid-cavity VCSEL.

We demonstrate a short-wavelength hybrid-cavity vertical-cavity surface-emitting laser (VCSEL) heterogeneously integrated on silicon. A GaAs-based "half-VCSEL" has been attached to a dielectric distributed Bragg reflector (DBR) on a silicon wafer using ultra-thin divinylsiloxane-bis-benzocyclobutene (DVS-BCB) adhesive bonding, thereby creating a cavity with the standing-wave optical field extending over the silicon- and GaAs-based parts of the cavity. A 9 µm oxide aperture diameter VCSEL with a threshold current of 1.2 mA produces 1.6 mW optical output power at 6.0 mA bias current with a wavelength of ~845 nm.

901 nm Lithographic vertical‐cavity surface‐emitting laser with stable single‐lobed beam pattern

Data are presented on 901 nm lithographic vertical-cavity surface-emitting lasers (VCSELs) demonstrating high efficiency for small VCSEL sizes, and stable beam patterns. Power conversion efficiency >40% is obtained for VCSELs ranging in size from 6 to 2 µm diameter. The 2 µm diameter VCSELs produce output powers in excess of 6.5 mW, and produce single-lobed far-field radiation patterns over the full range of operation.

Temperature-Dependent Impedance Characteristics of Temperature-Stable High-Speed 980-nm VCSELs

The temperature dependence of the impedance characteristics of high bit rate, highly temperature-stable 980-nm oxide-aperture vertical-cavity surface-emitting lasers (VCSELs) is investigated. A small-signal equivalent circuit model is fitted to measured small-signal reflection S11 and S21 scattering parameters across a large range of operating bias currents, temperatures, and oxide-aperture diameters to extract the circuit elements, −3 dB modulation bandwidth, relaxation resonance frequency, and parasitic cutoff frequency for each particular operating condition. The parasitic cutoff frequency of our small oxide-aperture diameter VCSELs is highly temperature insensitive from room temperature up to 85 °C, and does not limit our VCSELs’ maximum data transmission rate. Finally, the dependence of the impedance characteristics and modulation bandwidth of our VCSELs on the oxide-aperture diameter is analyzed at 25 °C and 85 °C. The larger capacitance is the main reason of our larger aperture VCSELs, compared with smaller aperture VCSELs, have a lower parasitic cutoff frequency.

Temperature-Stable 980-nm VCSELs for 35-Gb/s Operation at 85 °C With 139-fJ/bit Dissipated Heat

Energy-efficient oxide-confined 980-nm vertical-cavity surface-emitting lasers (VCSELs) operating at 35 Gb/s at 85 °C with only 139 fJ/bit of dissipated heat are reported. Oxide-aperture-dependent static characteristics and high-speed modulation properties at a high operation temperature of 85 °C are studied in detail. It is demonstrated that oxide-aperture diameters of ~3-4 μm are most suitable for energy-efficient and high bit rate operation at high temperatures. Data transmission experiments for ~3, 3.5, and 4 μm oxide-aperture diameter VCSELs are performed and the results are compared to formulate methods to minimize energy dissipation per bit. To date, our 980-nm VCSELs are the most energy-efficient VCSELs operating at 85 °C at any wavelength.

Small oxide‐free vertical‐cavity surface‐emitting lasers with high efficiency and high power

Data are presented showing high external differential quantum efficiency (DQE) and record-high output power in vertical-cavity surface-emitting lasers (VCSELs) with diameters below 3 µm. Good uniformity and reproducibility are achieved in devices with very small sizes. Over 75% DQEs are measured with maximum output powers of 5, 7.3, 8, 8.7 and 11.6 mW for 1, 1.5, 2, 2.5 and 3 µm diameter VCSELs, respectively.

Reliability performance of 25 Gbit s−1 850 nm vertical-cavity surface-emitting lasers

Multimode 850 nm vertical cavity surface-emitting lasers (VCSELs) suitable for high bit rate operation are studied. VCSELs with oxide aperture diameters of 5–7 µm show a high −3 dB modulation bandwidth (∼20 GHz) and D-factor (∼ 8 GHz mA−1/2). To allow low capacitance a multiple layer oxide-confined aperture design was applied. Eye diagrams are clearly open up to 35 Gbit s−1 at the temperature of 25 °C. Using 35 µm diameter PIN photodiodes and 6 µm oxide aperture diameter VCSELs error-free 25 Gbit s−1 (defined as a bit error ration of ≤1 × 10−12) optical fiber communication links were tested over 100 m of standard OM3 multimode optical fibers at 25 °C and 85 °C. The received optical power for error-free operation was below −4 dBm at both temperatures. A VCSEL reliability study at 95 °C was performed at the high current densities (∼18 kA cm−2) needed for error-free 25 Gbit s−1 operation at elevated temperatures. After 6000 h a slight increase (less than 5%) of the output optical power at a constant current was observed and most likely due to an ohmic contact burn in effect within the first 2000 h of the study. The results clearly indicate that 25 Gbit s−1 850 nm oxide-confined VCSELs with a complex AlGaO multilayer aperture design and with step-graded Al-compositions have the potential for reliable operation.

High-Speed Oxide Confined 850-nm VCSELs Operating Error-Free at 40 Gb/s up to 85<formula formulatype="inline"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula>

We present the temperature dependence of the performance characteristics of our latest generation high-speed oxide confined 850-nm vertical cavity surface-emitting lasers (VCSELs). Using a 7-μm oxide aperture diameter VCSEL, we demonstrate a maximum modulation bandwidth of ~ 27 GHz at room temperature and ~ 21 GHz at 85°C. With a new high-speed optical receiver, these bandwidths enable error-free data transmission (defined as a bit-error-rate <; 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> ) at bit-rates up to 47 Gb/s at room temperature, and up to 40 Gb/s at 85°C.

HIGH POWER AND HIGN BEAM QUALITY 980nm BOTTOM-EMITTING VERTICAL-CAVITY SURFACE-EMITTING LASER

A high-power and high beam quality 980nm bottom-emitting vertical-cavity surface-emitting laser (VCSEL) with optimized p-contact aperture was reported. A numerical simulation of current density in a large aperture bottom-emitting VCSEL with oxidation between the active region and the top p-type mirror was conducted. It is found that the simulated current density profiles of VCSEL are dependent on the oxide aperture diameter and the p-contact diameter. For a fixed oxide aperture diameter, the homogeneous current density of the VCSEL could he realized by optimizing the p-contact diameter. Thus, the edge mode in far-field patterns was suppressed. The far-field divergence angle from a 600 pm diameter VCSEL was suppressed from more than 30 to 15 and no strong sidelobe was observed in far-field pattern when the p-contact diameter decreased from 650 mu m to 580 mu m. There is a slight rise both in threshold current and optical output power due to the p-contact optimization. The VCSEL device produces the maximum optical output power of 2.01 W with lasing wavelength of 982.6nm by improving the device packaging method.

High-power vertical-cavity surface-emitting laser with an optimized p-contact diameter

A 980 nm bottom-emitting vertical-cavity surface-emitting laser (VCSEL) with a p-contact diameter is reported to achieve high power and good beam quality. A numerical simulation is conducted on the current spreading in a VCSEL with oxidation between the active region and the p-type distributed Bragg reflector. It is found that, for a particular oxide aperture diameter, somewhat homogeneous current distribution can be achieved for a VCSEL with an optimized p-contact diameter. The far-field divergence angle from a 600 microm diameter VCSEL is suppressed from 30 degrees to 15 degrees, and no strong sidelobe is observed in the far-field pattern by using the optimized p-contact diameter. There is a slight rise in threshold and optical output power that is due to the p-contact optimization. By improving the device packaging method, the maximum optical output power of the device is 2.01 W.

Linearly polarized bistable localized structure in medium-size vertical-cavity surface-emitting lasers

We show that a $40\text{\ensuremath{-}}\ensuremath{\mu}\mathrm{m}$-diameter vertical-cavity surface-emitting laser (VCSEL) is capable of supporting spatially localized structures with linear polarization, orthogonal to the principal polarization. The VCSEL is biased above the lasing threshold and emits a well-defined linear polarization (principal polarization). A holding beam with orthogonal polarization is injected into the cavity, and a localized structure is spontaneously switched on. The orthogonally polarized localized structure is shown to be bistable when the injection current is varied. Numerical results based on a rate equation model support the experimental findings.

Analog Modulation of 650-nm VCSELs

Small-signal properties of 650-nm vertical-cavity surface-emitting lasers (VCSELs) with different oxide aperture sizes were measured. A small diameter VCSEL of 3.5 mum has a maximum resonance frequency of 5.7 GHz. The photon density determines the maximum resonance frequency. Modeling also indicates higher photon densities in the small VCSEL due to better thermal behavior

High-power vertical-cavity surface-emitting laser with an extra Au layer

We report the performance of a high-power vertical-cavity surface-emitting laser (VCSEL) with an extra Au layer. By using the extra Au layer, the far-field divergence angle from a 600-μm diameter VCSEL device is suppressed from 30/spl deg/ to 15/spl deg/, and no strong sidelobe is observed in far-field pattern. There is a slight drop in optical output power due to the introduction of the extra Au layer. By improving the device packaging method, the VCSEL device produces the maximum continuous-wave optical output power of 1.95 W with lasing wavelength of 981.5 nm. The aging test is carried out under constant current mode at 60/spl deg/C, and the preliminary result shows that the total degradation of output power is less than 10% after 800 h.

Improvement in Light Output of Thin-Film Vertical-Cavity Surface-Emitting Lasers Transferred onto A1N Substrates

Thin-film 850-nm vertical-cavity surface-emitting lasers (VCSELs) were improved in light output power by designing both the reflectivity of the distributed Bragg reflector on the light-emitting side and also the degree of de-tuning between the photoluminescence peak and the etalon wavelength. Thin-film VCSELs, which were fabricated on A1N substrates by a functional layer transfer technique, are attractive components for the hybrid integration of optoelectronic devices. Their maximum output power was 2.8 mW and their slope efficiency was 0.40 W/A for the 15μm diameter VCSEL devices that we studied. Uniform spontaneous emission over the entire mesa area, and a single transverse laser mode up to 1.3 times the threshold current were confirmed by observing the near-field images.

Cryogenic operation of AlGaAs-GaAs vertical-cavity surface-emitting lasers at temperatures from 200 K to 6 K

We demonstrate for the first time the CW performance of AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) at cryogenic temperatures from 6 K to 200 K. By detuning the cavity mode with respect to the gain peak so that optimum dc lasing operation is achieved at -100 K, we find that this optimum lasing performance can be maintained down to temperatures as low as 6 K. Across a broad range of temperatures from 200 K to 6 K, the minimum threshold current of a 16-/spl mu/m diameter VCSEL stayed below 4 mA, while its -3-dB modulation bandwidth increased by about 70% to 11 GHz at 6 K, and the external slope efficiency is greater than 70%.

1.55 [micro sign]m vertical-cavity surface-emitting lasers with wafer-fused InGaAsP/InP-GaAs/AlAs DBRs

The authors propose a novel 1.55 µm vertical-cavity surface-emitting laser (VCSEL) structure with wafer-fused InGaAsP/InP-GaAs/AlAs distributed Bragg reflectors. The resonant-cavity wavelength before water fusion is in exact accord with the emission wavelength, and a 25 µm diameter VCSEL exhibits CW operation at 27°C.

Single-mode, passive antiguide vertical cavity surface emitting laser

We report the characteristics of a single-mode, low threshold, passive antiguide region (PAR) vertical cavity surface emitting laser (VCSEL) using both organometallic chemical vapor deposition (OMCVD) and molecular beam epitaxy (MBE) for the regrowth of the PAR structure. The novel passive antiguide region surrounding the active region is demonstrated to be a highly effective transverse mode and polarization mode selection mechanism. A stable single fundamental mode at high currents has been achieved experimentally for laser aperture as large as 16 /spl mu/m diameter, In addition, very low threshold current of 0.8 mA and current density of 490 A/cm/sup 2/ are achieved with 8 and 32 /spl mu/m diameter VCSEL's, respectively. A detailed numerical two- and three-dimensionaI analysis was performed using the beam propagation method. The modal losses were calculated as a function of the cladding refractive index and the laser size. Quantitative results leading to approximate formulae have been achieved. The high mode selectivity obtained from the numerical analysis is in good agreement with the experimental results we have achieved. >