Tunable DBR Laser Research Articles

MOVPE growth of tunable DBR laser diode emitting at 1060 nm

Tunable laser diodes emitting at 1060 nm have been grown by metalorganic vapor-phase epitaxy (MOVPE). For the growth of the highly strained InGaAs/GaAs quantum well (QW) high growth rates are found favorable to suppress defect formation. Laser diodes using such QWs in GaAs waveguide and AlGaAs cladding layers show very low threshold ( j th=104 mA) and transparency current densities ( j T=53 A cm −2). These low values are preserved when the growth is interrupted after the upper GaAs waveguide and a grating is processed. Three sectional laser diodes having a distributed Bragg reflector grating section, a phase shift and a gain section have a very small linewidth of 0.85 MHz at 30 mW and a tuning range of 300 GHz.

Tunable sampled-grating DBR lasers with integrated wavelength monitors

We report on the design and development of a wavelength monitor for use with tunable semiconductor lasers. The device is based on two-mode interference in an asymmetrically excited waveguide that is coupled to a Y-branch splitter. The monitoring range of the device is 30 nm. The wavelength monitor is capable of operating over an input power range of 34 dB, and the waveguide detectors do not saturate at photocurrents as high as 1.2 mA. The sensitivity of the monitor is only 1.24 nm for an isolated device, but improves to 0.44 nm when it is integrated on chip with the laser.

Virtual wavelength path cross-connect based on optoelectronic wavelength conversion

This paper describes the system design and performance of a virtual wavelength path cross-connect (VWP-XC); we demonstrate its function of wavelength conversion, cross-connection, and transportation. We realize a feasible wavelength conversion technique using an optical receiver and a tunable DBR laser. Frequency stability of a 100 GHz-spaced wavelength-converted signal is confirmed by a multiwavelength simultaneous monitoring circuit (MSMC) to be within 100 MHz. VWP cross-connection and error free transportation over 160 km and four 120 km spans (480 km with 3 repeaters) is confirmed in a five-node VWP network.

Frequency noise and modulation of a four-section DBR laser

A theoretical model is presented to describe the tuning, frequency noise, and modulation characteristics of tunable DBR lasers with two active and two passive sections. Analytical expressions are derived for the intensity and frequency modulation responses, frequency noise spectrum, spectral linewidth, effective linewidth enhancement factor, and spontaneous emission rate. It is shown that a nearly flat red-shifted FM response over several gigahertz can be obtained by nonuniform current injection and modulation of the lower carrier density section in the active region. Increasing the tuning current through the passive sections enhances the FM efficiency. However, a higher FM efficiency is generally accompanied by a larger spectral linewidth. The predictions of our theoretical model are in good agreement with the available experimental data.

High number of wavelength channels demonstrated by a widely tunable sampled-grating DBR laser

A three-section sampled-grating DBR laser has been realised. It presents a 25 nm tuning range with an SMSR greater than 30 dB. For the first time with sampled reflectors, access to 22 wavelength channels is achieved thanks to discontinuous tuning among the five main reflection peaks of the comb-reflection spectra of the sampled gratings. Operation of this device under amplitude modulation is also discussed: an AM bandwidth greater than 2.5 GHz has been demonstrated.

Frequency stabilization of tunable DBR laser using multiwavelength light injection locking technique

This paper proposes a frequency stabilization scheme for tunable three-section DBR laser diodes (3S-DBR LD) that use multiwavelength light injection locking. The oscillating wavelength of the SS-DBR LD is discretely switched between cavity modes when the injection current into DBR section is changed, and locked to one wavelength of the multiwavelength light injected from the DBR section facet under the injection locking condition. The light injection properties of the capture range and the relationships of relaxation oscillation versus input power and detuning are investigated experimentally. Injection locking on the multistate wavelength of a tunable DBR LD is performed using a two wavelength multiplexed light. As a result, we demonstrate 1 GHz capture range and more than 26 dB rejection ratio for the multiplexed injected light.

Wavelength optical/electronic encoding module for ATM optical-switching

We present a novel wavelength-encoding module, suitable for high-speed wavelength switching in wavelength-division multiplexing (WDM) networks. This module includes a tunable DBR laser and an original GaAs IC-driver, which is a full custom 0.5-/spl mu/m gate-length P-HEMT IC. With fast switching time (300 ps), low power consumption (1.4 W), and small dimensions, this tunable-driver advantageously replaces the conventional electronics. Switching over four wavelength-modes has been demonstrated with parasitic wavelength-drifts lower than 0.02 nm, and switching times are mainly laser dependent. Implementation of the module inside a 4/spl times/4 ATM switching-matrix demonstrator working at 2.5 Gbit/s shows no degradation of the EER. >

Analysis of FM and AM responses of a tunable three-electrode DBR laser diode

Starting with the wave propagation equation, neglecting spatial and spectral hole-burning effects, and using a solving method based on the Green's function, the rate equations are derived for a multielectrode laser. By applying them to a three-electrode DBR laser, tunability and linewidth performance are evaluated, and the modulation characteristics such as the amplitude response and the frequency response are analyzed. It is shown that amplitude modulation can be completely suppressed, and at the same time, a pure frequency modulation obtained if currents are related by an adequate equation. Since this laser diode has many advantages such as a wide wavelength tunability and a narrow spectral linewidth, it will be suitable as a lightwave oscillator or transmitter in future communication systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Delayed self-multiplex light source for frequency-agile transmitters

The delayed self-multiplex (DSM) light sources proposed in this paper provide multiple frequency-agile outputs from a single tunable laser. The DSM light source employs multiple fiber delay lines and optical switches, and overcomes the intrinsic tuning-speed limitation and thermal frequency drift of the tunable laser. Practical switching performance restricted by the optical switch is analyzed and examined in a delayed self-duplex (DSD) light source constructed with a tunable DBR laser and a LiNbO/sub 3/ electrooptic switch. Bit-error-free operation of the frequency-agile transmitter is achieved in 622 Mb/s transmission; the power penalty due to the DSD light source is 1.8 dB.

Dynamic wavelength tuning characteristics of the 1.5-μm three-section DBR lasers: analysis and experiment

We present a detailed theoretical analysis of the static and dynamic tuning characteristics of 1.55-/spl mu/m region three-section tunable DBR lasers under discrete tuning and under continuous tuning. We have analyzed the oscillating wavelength, the Bragg wavelength, and output power characteristics using the rate equation that considers the thermal effect, simultaneously analyzed the heat transfer equation, considering the heat transfer among passive waveguides, the LD chip, the submount, and the heat sink. We experimentally confirm the static and dynamic wavelength tuning characteristics using a highly accurate heterodyne measurement system. Static and dynamic characteristics simulated using the three-section DBR laser model and the thermal model agree with the experimental results presented in this paper.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Monolithically integratedpolarisation diversity heterodyne receivers on GaInAsP/InP

Polarisation diversity heterodyne receiver OEICs including a tunable four-section DBR laser as a focal oscillator have been successfully fabricated for the first time. OEIC design and fabrication are described and first characteristics of the integrated subcomponents and a packaged receiver OEIC are presented.

Modelling and performance analysis of an opticalfrequency feedbackloop for tunable DBR laser diodes with fast current switching

A simple linear equivalent circuit of an optical frequency feedback loop is introduced to reduce the thermal drift associated with current switching in three-section DBR laser diodes. Numerical analysis of the proposed circuit reveals design tradeoffs existing among several performance categories of the loop. An optimum design for the loop is then presented.

Increased modulation bandwidth up to 20 GHz of a detuned-loaded DBR laser

A small signal amplitude modulation bandwidth of 20 GHz has been obtained with a three-section tunable DBR laser fabricated with semi-insulating current blocking layers grown by hydride VPE. The modulation bandwidth and laser linewidth are strongly dependent on the position of the lasing mode relative to the Bragg reflection peak. >

Fast and stable frequency switching employing a delayed self-duplex (DSD) light source

A novel frequency-agile light source, the delayed self-duplex (DSD) light source, is constructed using a tunable DBR laser and an optical switch. The DSD light source overcomes the tuning speed limitation of the tunable laser, and also offers suppressed frequency drift due to the thermal effect by employing periodic laser tuning. For 160-GHz-spaced frequency switching, the 4-ns switching time and 2.2-GHz thermal frequency drift inherent to the DBR laser are reduced to 0.4 ns and 0.3 GHz, respectively. >

Super-structure-grating (SSG) for broadly tunable DBR lasers

The reflection characteristics of super-structure-grating (SSG) reflectors are demonstrated theoretically and experimentally. The periodic multireflection peaks with high reflectivities of 68 approximately 98% are theoretically shown in the reflection spectrum. The experimental characteristics of a ridge-type SSG reflector are in good agreement with the theoretical design.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Over 100 nm wavelength tuning in superstructure grating (SSG) DBR lasers

A broad range tuning of over 100 nm in tunable DBR lasers with superstructure grating (SSG) is reported. The SSG reflectors for 100 nm were designed and patterned by electron beam lithography. 1.55 μm DBR lasers with SSG reflector operate in a single mode with a tuning range of 83 nm under CW conditions. With inclusion of the multimode operating region, the tuning range becomes as wide as 103 nm.

Stimulated emission in Er:Ti:LiNbO 3 channel waveguides close to 1.53 μm transition

Fabrication and characterisation of Er:Ti:LiNbO3 channel waveguides is reported. A lifetime of 2.4±0.2 ms has been measured for the 4I13/2 level. In a pump and probe experiment using a high power InGaAsP laser and a tunable DBR laser, a signal increase of 0.75 dB for a transmitted pump power of 4.8 mW was demonstrated.

Influence of leakage currents between electrodes in tunable DBR-lasers

Wavelength tunable multi-section DBR lasers have been fabricated on a p-doped InP substrate by LPE. Maximum output power is 10.5 mW and largest step-wise tuning range is 5.1 nm for a single-sided DBR laser. A double-sided laser has a continuous tuning range of 1.4 nm. It is shown that the low electrical isolation between the top contacts causes lower output power and a significantly larger laser linewidth.

Fast wavelength switching and simultaneous FSK modulation using tunable DBR laser

This letter describes the operation of a tunable three-section DBR laser for multiwavelength switching with up to 48 resolvable wavelengths. Fast switching among wavelengths that are spaced over a 2.2 nm continuous tuning range and simultaneous FSK data modulation of each channel are demonstrated. A novel wide-deviation FSK modulation scheme to reduce temperature induced wavelength drifts is also described.

Tunable DBR laser with wide tuning range

Characteristics of a 1.55 mu m wavelength tunable DBR laser with three sections are described. The wavelength tuning range is investigated by changing the composition of the GaInAsP guide layer. The maximum change of the Bragg wavelength is nearly 10 nm at lambda /sub g/=1.38 mu m, and a continuous tuning range of 6.2 nm is achieved for lambda /sub g/=1.29 mu m.