Waveguide DFB Research Articles

Direct modulation bandwidth enhancement of uncooled DFB laser operating over a wide temperature range based on groove-in-trench waveguide structure

Uncooled direct modulation DFB laser offers high speed transmission rate over a wide temperature range with high reliability and low cost, making it a cost-effective light source choice for 5G fronthaul and data center applications. However, a significant 3dB bandwidth decrease can be observed in high temperature for conventional DFB lasers. We present an uncooled DFB laser operating up to 85°C with extended direct modulation bandwidth and high reliability based on a novel groove-in-trench ridge waveguide structure, where two narrow grooves penetrating the active layer are etched symmetrically in the two conventional trenches by deep wet etching, respectively. By optimizing the distance between the groove and the mesa stripe, we obtain a 3dB bandwidth of 15.3 GHz at 85°C, which is a 3.7 GHz improvement compared with the conventional ridge waveguide DFB laser. Transmissions of 25 Gb/s NRZ signal at 25°C and 85°C with clear eye openings have been demonstrated. It also achieves 25 Gb/s transmission over 10 km optical fiber with a low power penalty of 0.5 dB for a bit error rate of 10-12 at 85°C. In addition, the result of 2000-hour aging test shows that the proposed groove-in-trench structure DFB lasers have the same excellent reliability as the conventional ones.

Potential for sub-mm long erbium-doped composite silicon waveguide DFB lasers

Compact silicon integrated lasers are of significant interest for various applications. We present a detailed investigation for realizing sub-mm long on-chip laser structures operating at λ = 1.533 µm on the silicon-on-insulator photonic platform by combining a multi-segment silicon waveguide structure and a recently demonstrated erbium-doped thin film deposition technology. Quarter-wave shifted distributed feedback structures (QWS-DFB) are designed and a detailed calculation of the lasing threshold conditions is quantitatively estimated and discussed. The results indicate that the requirements for efficient lasing can be obtained in various combinations of the designed waveguide DFB structures. Overall, the study proposes a path to the realization of compact (< 500 µm) on-chip lasers operating in the C-band through the hybrid integration of erbium-doped aluminum oxide processed by atomic layer deposition in the silicon photonic platform and operating under optical pumping powers of few mW at 1,470 nm.

Enhancement of Amplified Spontaneous Emission and Laser Performance of Rhodamine 6G/Cellulose Acetate DFB and DBR Waveguide Devices: A Role of Thermally Annealed P(VDF-TrFE) Intermediate Layer

Inserting a crystalline P(VDF-TrFE) intermediate layer under rhodamine 6G (R6G) laser active waveguide layer preserved the emissive R6G molecules in the matrix, which increases the intensity of flu...

A Sub-kHz Narrow-Linewidth, and Hundred-mW High-Output-Power Silicon-Based Er Silicate Laser With Hybrid Pump and Signal Co-Resonant Cavity

Narrow-linewidth silicon-based lasersplay an important role in the field of silicon photonics. In this paper, we have proposed a high performance narrow-linewidth silicon-based Er silicate laser, based on strip-loaded DFB waveguide with a hybrid pump and signal co-resonant cavity. The saturated output power can reach over 90 mW at 1535 nm, with a maximum power conversion efficiency of 66%. The pump threshold is about 22 mW, and the laser linewidth is also as narrow as about 755 Hz. The results provide a new way for future scale integrated ultra-narrow-linewidth silicon-based lasers application.

A horn ridge waveguide DFB laser with reduced spatial hole burning for high-speed modulation

In this paper, we propose a DFB laser with a horn ridge waveguide (HRW) to suppress the longitudinal spatial hole burning (LSHB) effect in the lasers cavity, thus to reduce the rolloff at low frequency. The simulation result shows that HRW DFB lasers could significantly suppress the LSHB effect and its modulation bandwidth is increased by 14% comparing with the conventional straight ridge waveguide (RW) DFB lasers when the normalized coupling coefficient (κL) is 3.0. The calculated eye diagrams of HRW DFB lasers under direct 25 Gbps modulation have clearer opening than that of the conventional RW DFB lasers. These superior properties are due to the suppression of the LSHB effect by the HRW structure.

Erbium-doped waveguide DBR and DFB laser arrays integrated within an ultra-low-loss Si_3N_4 platform

Record low optical threshold power and high slope efficiency are reported for arrays of distributed Bragg reflector lasers integrated within an ultra-low-loss Si(3)N(4) planar waveguide platform. Additionally, arrays of distributed feedback laser designs are presented that show improvements in pump-to-signal conversion efficiency of over two orders of magnitude beyond that found in previously published devices. Lithographically defined sidewall gratings provide the required lasing feedback for both cavity configurations. Lasing emission is shown over a wide wavelength range (1534 to 1570 nm), with output powers up to 2.1 mW and side mode suppression ratios in excess of 50 dB.

Optimization of 780 nm DFB diode lasers for high-power narrow linewidth emission

We demonstrate the realization of narrow linewidth, high-power ridge waveguide DFB diode lasers emitting near 780 nm. The effects of the coupling coefficient, the laser chip length, and the fabrication process onto the spectral linewidth are discussed. By optimizing both the cavity length and the coupling coefficient, we achieve an intrinsic spectral linewidth as small as 35 kHz at an output power of 270 mW.

Integration of a Rib Waveguide Distributed Feedback Structure into a Light‐Emitting Polymer Field‐Effect Transistor

AbstractAmbipolar light‐emitting organic field‐effect transistors (LEFETs) possess the ability to efficiently emit light due to charge recombination in the channel. Since the emission can be made to occur far from the metal electrodes, the LEFET structure has been proposed as a potential architecture for electrically pumped organic lasers. Here, a rib waveguide distributed feedback structure consisting of tantalum pentoxide (Ta2O5) integrated within the channel of a top gate/bottom contact LEFET based on poly(9,9‐dioctylfluorene‐alt‐benzothiadiazole) (F8BT) is demonstrated. The emitted light is coupled efficiently into the resonant mode of the DFB waveguide when the recombination zone of the LEFET is placed directly above the waveguide ridge. This architecture provides strong mode confinement in two dimensions. Mode simulations are used to optimize the dielectric thickness and gate electrode material. It is shown that electrode absorption losses within the device can be eliminated and that the lasing threshold for optical pumping of the LEFET structure with all electrodes (4.5 µJ cm−2) is as low as that of reference devices without electrodes. These results enable quantitative judgement of the prospects for realizing an electrically pumped organic laser based on ambipolar LEFETs. The proposed device provides a powerful, low‐loss architecture for integrating high‐performance ambipolar organic semiconductor materials into electrically pumped lasing structures.

Multiwavelengths DFB waveguide laser arrays in Yb-Er codoped phosphate glass substrate

The realization of arrays of 15 distributed feedback lasers integrated on an Er-Yb-doped phosphate glass substrate is reported. A submicronic corrugated grating has been etched on a comb of Ag/sup +/-Na/sup +/ ion exchanged waveguides with varying diffusion aperture width. Robust single frequency emission spectrum are shown, closely gauged on the 25- and 100-GHz International Telecommunications Union grids around 1.535 μm with a pump-power threshold of 14 mW and a slope efficiency of 5.7%.

10 Gbit/s transmission using directly modulated uncooled MQW ridge waveguide DFB lasers in TO package

Direct modulation at 10 Gbit/s and uncooled operation of a MQW ridge waveguide laser at 1.3 /spl mu/m is demonstrated. Transmission experiments over 10 km at room temperature and over 4 km at a transmitter case temperature of 65/spl deg/C over standard singlemode fibre have been performed. Both transmitter and receiver are packaged into standard TO46 cases, thus offering low-cost potential for future high-speed datacom applications.

High power narrow divergence DFB laser diode at 1.55 [micro sign

Over 115 mW single longitudinal mode laser output was obtained from an InGaAsP MQW DFB waveguide laser diode integrated with a vertically tapered mode expander. The circular cross-sectional laser beam profile with the FWHM divergence angles of 9.5/spl deg//spl times/13.5/spl deg/ enabled a high coupling efficiency of 63% directly into a lensed singlemode fibre, resulting in a fibre coupled output of over 70 mW.

A ridge waveguide DFB laser model including transverse carrier and optical effects

In this paper, a steady-state model for ridge waveguide DFB lasers is presented. The complex two-dimensional semivectorial optical mode in the transverse direction is solved using a finite difference scheme without introducing any approximations. The electron and hole diffusion in the lateral direction is also considered, Along the longitudinal direction, a novel "Superposition of Spectral Power Method" is used, based on the coupled mode formulation. This model enables one to examine the interaction between the optical and carrier profiles for different injection levels and arbitrary transverse index profiles. As such, it is useful for studying CW characteristics such as lasing wavelength and threshold current. Finally, the results from this model are compared with experimental data from a varying ridge width laser array fabricated from a 1.55 /spl mu/m InGaAsP-InP compressively strained multiquantum-well loss-coupled DFB structure.

Distributed feedback lasers with an S-bent waveguide for high-power single-mode operation

DFB lasers with variations in the Bragg wavenumber along the cavity (corrugation-pitch modulation) can be designed to operate in a single mode up to high output powers. Practical implementation of various pitch-modulated DFB cavities is facilitated by bending the laser waveguide over a uniform grating, so that the Bragg wavenumber is varied along the cavity. In this paper, above-threshold behavior of such lasers is studied, and design rules for high power single-mode operation are developed. S-bent waveguide DFB lasers, fabricated according to our design criteria, exhibit single-mode operation with 40 dB side mode suppression ratio from threshold to 10/spl times/I/sub th/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

DFB and DBR lasers emitting at 980 nm

The performance of DFB and DBR ridge waveguide lasers operating at 980 nm is reported. The DBR devices used a single growth step and gave singlemode output powers as high as 30 mW. The DFB devices used a two-step growth process in which the lower cladding and active regions were grown first, the gratings were etched and then the upper cladding and p-contact layers were regrown on top of the grating. The DFB devices gave output powers as high as 75 mW.

Clock recovery based on a new type of selfpulsation in a 1.5 μm two-section InGaAsP-InP DFB laser

Clock extraction from an optically or electrically injected 223 − 1 PRBS RZ data signal in a two-section ridge waveguide DFB laser with a new type of selfpulsation is demonstrated between 0.4 and 0.7 GHz. A locking range of 50 MHz is measured.

DFB lasers with monolithically integrated passive waveguide

Novel MQW integrated passive waveguide (IPW) DFB lasers have been fabricated using a selective area MOVPE growth technique. Detailed measurements of the absorption loss of the passive waveguide in the structure as well as its influences on the laser linewidth are reported for the first time. A linewidth reduction factor of more than 3 is observed as compared to a simple DFB laser despite the high absorption loss. >

Optical properties of metal-clad/Pb1−xSnxTe waveguides

The optical characteristics of a metal/p-Pb1−xSnxTe/p+-Pb1−xSnxTe three layers waveguide were studied. The effective index, propagation losses and electric field distribution of the TE-modes were calculated numerically. Approximate expressions for the losses derived by first-order perturbation methods were found to agree with the exact solutions. The conditions for transversal and lateral single-mode operation of the waveguide were discussed. The coupling constant of a metal/Pb1−xSnxTe DFB waveguide produced by periodic variation in the active layer thickness and on-off metal contact modulation was calculated by the perturbation technique.

Simple determination of coupling coefficient in DFB waveguide structures

A simple method allowing the determination of the coupling coefficient Kq of DFB waveguide structures of arbitrary type, number of layers and grating profile is proposed. The method relies on effective index determination and the fast Fourier transform of the actual grating profile. The method has been validated by comparison with the measured stopband width of liquid phase epitaxy (LPE) and gas source molecular beam epitaxy (GSMBE) grown 1.5μm DFB lasers.

Stabilisation of oscillation frequency of an AlGaAs/GaAs ridge waveguide distributed feedback laser

Oscillation frequency of an AlGaAs/GaAs ridge waveguide DFB laser is stabilised without temperature control. The frequency fluctuation is suppressed to less than±5 MHz for a temperature change of 0.1 deg C.

Anomalous modal spectrum of radiation of DFB and DBR lasers

The modal spectrum of waveguide DFB and DBR lasers is examined theoretically. It is founf that the modal spectrum of the laser output can differ greatly from the spectrum inside the laser cavity. Numerical results are presented for examples of DFB and DBR lasers.