Laser Diode Driver Research Articles

A 155 Mbps laser diode driver with automatic power and extinction ratio control

An integrated laser diode driver (LDD) driving an edge-emitting laser diode was designed and fabricated by 0.35 μm BiCMOS technology. This paper proposes a scheme which combines the automatic power control loop and temperature compensation for modulation current in order to maintain constant extinction ratio and average optical power. To implement temperature compensation for modulation current, a novel circuit which generates a PTAT current by using the injecting base current of a bipolar transistor in saturation region, and alternates the amplifier feedback loop (closed or not) to control the state of the current path is presented. Simulation results showed that programmed by choice of external resistors, the IC can provide modulation current from 5 mA to 85 mA with temperature compensation adjustments and independent bias current from 4 mA to 100 mA. Optical test results showed that clear eye-diagrams can be obtained at 155 Mbps, with the output optical power being nearly constant, and the variation of extinction ratio being lower than 0.7 dB.

A digitally controlled on-chip monotonic reference current generator with low LSB current for fast and accurate optical level monitoring

This paper describes a digitally controlled on-chip monotonic Reference Current Generator (RCG) with 8-bit resolution and a LSB (Least Significant Bit) current as low as 100 nA. It was designed as a building block of a generic DC-coupled Burst Mode Laser Diode Driver (BM-LDD) for GPON (Gigabit Passive Optical Network) applications and acts as an on-chip RCG with a settling time of 18 ns for fast and accurate optical level monitoring with guaranteed monotony. The proposed architecture of the on-chip RCG is based on an 8-bit segmented current-steering Digital-to-Analog Converter (IDAC) and a bandgap voltage reference. The (3 + 5) segmented architecture of the 8-bit IDAC is an optimum combination of a 3-bit MSBs (Most Significant Bits) unit-element sub-DAC and a 5-bit LSBs binary-weighted sub-DAC offering good DNL (Differential Nonlinearity) performance. The bandgap voltage reference deviates only 0.6% of the nominal value over temperature and power supply variations. A cascade current mirror with a super beta helper circuit is used to guarantee monotony and high accuracy. The linearity errors caused by systematic influences and random variations are reduced by the proposed 2-D double centroid symmetrical architecture. Experiments confirm a DNL of ±0.5 LSB for the proposed RCG. The tested performance of optical level monitoring and APC (Automatic Power Control) algorithm is compliant to ITU-T GPON standards. The design was realized in a 0.35 μm SiGe BiCMOS technology with 3.3 V power supply. The technology choice was made by heavy requirements of the innovative DC-coupled 1.25 Gbit/s BM-LDD chip. Although the proposed structure was designed as a building block for a BM-LDD chip, the design concept can be applied for developing other high linearity on-chip RCG for a wide junction temperature range (?40 to 110°C).

A 1.25 Gbps DC-coupled laser diode driver with VBE compensation technique

A 1.25Gbps integrated laser diode driver (LDD) driving an edge-emitting laser has been designed and fabricated in 0.35μm BiCMOS technology. The IC can provide independent bias current (5–100mA) with automatic power control, and modulation current (4–85mA) with temperature compensation adjustments to minimize the variation in extinction ratio. This paper proposed an unique modulation output driver configuration which is capable of DC-coupling a laser to the driver at +3.3V supply voltage; and combined a VBE compensation circuit, the IC can operate at a wide temperature range (−40 to 85°C) for date rates up to 1.25Gbps. VBE compensation technique is used to compensate for variation in VBE over the operating temperature range so as to minimize the variations in rise and fall time of modulation output over temperatures.

DC-Coupled Burst-Mode Laser Diode Driver with Automatic Power Control for 1.25Gbit/s PON System

An integrated burst-mode laser diode driver is presented for PON application. The bias current range and modulation current range are 1---75 mA and 5---80 mA respectively. The DC-coupled interface ...

Analysis and Design of an LCL-T Resonant Converter as a Constant-Current Power Supply

An LCL-T resonant converter (LCL-T RC) is shown to behave as a current source when operated at resonant frequency. A detailed analysis of the LCL-T RC for this property is presented. Closed-form expressions for converter gain, component stresses, and the condition for converter design optimized for minimum size of resonant network is derived. A design procedure is illustrated with a prototype 200-W 20-A current-source power supply and experimental results are presented. The LCL-T RC as a current source offers many advantages such as easy parallel operation and low circulating currents at light load. Additionally, with appropriate phase shift in paralleled modules, the peak-peak ripple in output current is reduced and the ripple frequency is increased, reducing filtering requirements. The leakage inductance of a transformer can be advantageously integrated into the resonant network. These merits make the topology applicable in various applications such as magnet power supply, capacitor charging power supply, laser diode drivers, etc.

Focus on Lasers and Optics

Focus on Lasers and Optics

Design and testing of low intensity laser biostimulator

BackgroundThe non-invasive nature of laser biostimulation has made lasers an attractive alternative in Medical Acupuncture at the last 25 years. However, there is still an uncertainty as to whether they work or their effect is just placebo. Although a plethora of scientific papers published about the topic showing positive clinical results, there is still a lack of objective scientific proofs about the biostimulation effect of lasers in Medical Acupuncture. The objective of this work was to design and build a low cost portable laser device for stimulation of acupuncture points, considered here as small localized biosources (SLB), without stimulating any sensory nerves via shock or heat and to find out a suitable method for objectively evaluating its stimulating effect. The design is aimed for studying SLB potentials provoked by laser stimulus, in search for objective proofs of the biostimulation effect of lasers used in Medical Acupuncture.MethodsThe proposed biostimulator features two operational modes: program mode and stimulation mode and two output polarization modes: linearly and circularly polarized laser emission. In program mode, different user-defined stimulation protocols can be created and memorized. The laser output can be either continuous or pulse modulated. Each stimulation session consists of a pre-defined number of successive continuous or square pulse modulated sequences of laser emission. The variable parameters of the laser output are: average output power, pulse width, pulse period, and continuous or pulsed sequence duration and repetition period. In stimulation mode the stimulus is automatically applied according to the pre-programmed protocol. The laser source is 30 mW AlGaInP laser diode with an emission wavelength of 685 nm, driven by a highly integrated driver. The optical system designed for beam collimation and polarization change uses single collimating lens with large numerical aperture, linear polarizer and a quarter-wave retardation plate. The proposed method for testing the device efficiency employs a biofeedback from the subject by recording the biopotentials evoked by the laser stimulus at related distant SLB sites. Therefore measuring of SLB biopotentials caused by the stimulus would indicate that a biopotential has been evoked at the irradiated site and has propagated to the measurement sites, rather than being caused by local changes of the electrical skin conductivity.ResultsA prototype device was built according to the proposed design using relatively inexpensive and commercially available components. The laser output can be pulse modulated from 0.1 to 1000 Hz with a duty factor from 10 to 90 %. The average output power density can be adjusted in the range 24 – 480 mW/cm2, where the total irradiation is limited to 2 Joule per stimulation session. The device is controlled by an 8-bit RISC Flash microcontroller with internal RAM and EEPROM memory, which allows for a wide range of different stimulation protocols to be implemented and memorized. The integrated laser diode driver with its onboard light power control loop provides safe and consistent laser modulation. The prototype was tested on the right Tri-Heater (TH) acupuncture meridian according to the proposed method. Laser evoked potentials were recorded from most of the easily accessible SLB along the meridian under study. They appear like periodical spikes with a repetition rate from 0.05 to 10 Hz and amplitude range 0.1 – 1 mV.ConclusionThe prototype's specifications were found to be better or comparable to those of other existing devices. It features low component count, small size and low power consumption. Because of the low power levels used the possibility of sensory nerve stimulation via the phenomenon of shock or heat is excluded. Thus senseless optical stimulation is achieved. The optical system presented offers simple and cost effective way for beam collimation and polarization change. The novel method proposed for testing the device efficiency allows for objectively recording of SLB potentials evoked by laser stimulus. Based on the biopotential records obtained with this method, a scientifically based conclusion can be drawn about the effectiveness of the commercially available devices for low-level laser therapy used in Medical Acupuncture. The prototype tests showed that with the biostimulator presented, SLB could be effectively stimulated at low power levels. However more studies are needed to derive a general conclusion about the SLB biostimulation mechanism of lasers and their most effective power and optical settings.

High-speed DVD-multi drive system

High speed DVD-RAM and DVD-R recording technologies have been established for the DVD-multi drive system. The developed key components are LSIs, especially a laser diode driver, and an optical pickup.

Highly compact and efficient femtosecond Cr:LiSAF lasers

Methods for developing more compact femtosecond Cr:LiSAF laser sources are examined. By careful modeling of the low threshold performance and intracavity dispersion characteristics of these cavities, a highly asymmetric z-cavity design with a single prism for dispersion compensation is developed. Transform-limited pulses as short as 113 fs and modelocked output powers up to 20 mW are demonstrated for less than 110 mW of laser-diode pump power. The complete laser system (including the laser diode pump system and drivers) has a footprint of 21.5 /spl times/ 28 cm/sup 2/, about the size of a sheet of US letter or A4 paper.

A novel simplified laser diode driver

A novel, low-cost, and simple circuit for driving a laser diode with low supply voltage was demonstrated. A laser diode was driven with a supplied voltage as low as 1.5 V using only two transistors and minimum passive components.

An analog front-end chip set employing an electro-optical mixed design on SPICE for 5-Gb/s/ch parallel optical interconnection

A chip set composed of a laser-diode driver (LDD) and an optical receiver (RCV), which incorporates a full 2D (reshape, regenerate) function, has been developed by using silicon bipolar technology for a four-channel 5-Gb/s parallel optical transceiver. An electro-optical mixed design on SPICE of the LDD and the LD is accomplished by describing the rate equations of the LD as an electrical circuit. This design accommodates easy connectivity of the LDD chip to the LD in the optical transmitter module without the need for adjustment of the optical waveform. A pseudobalanced transimpedance amplifier (TIA) and feedforward automatic decision threshold control (ATC) in the RCV minimize the number of off-chip bypass capacitors, eliminate the need for any off-chip coupling capacitors, and keep crosstalk less than -50 dB and low cutoff frequency less than 80 kHz. A prototype parallel optical transmitter module and a prototype receiver module, based on the chip set, demonstrated asynchronous four-channel 5-Gb/s operation. The chip set has a throughput of 20 Gb/s with a power dissipation of 1.3 W at a 3.3-V supply.

Atomic spectroscopy with violet laser diodes

Laser spectroscopy with laser diodes can now also be performed in the violet/blue spectral region. A 5 mW commercially available CW laser diode operating at 404 nm was used to perform spectroscopy on potassium atoms with signal detection in absorption as well as fluorescence when operating on a potassium vapor cell and with optogalvanic detection on a potassium hollow cathode lamp. The 4s 2S1/2–5p 2P3/2,1/2 transitions were observed at 404.5 and 404.8 nm, respectively. The laser diode was operated with a standard laser diode driver, and with or without an external cavity. The 4s 2S1/2–4p 2P1/2 transition at 770.1 nm was also observed with a different laser diode. Here, Doppler-free saturated-absorption signals were also observed, enabling the evaluation of the ground-state hyperfine splitting of about 460 MHz. The data recorded allows an experimental verification of the theory for Doppler broadening at two widely separated wavelengths.

Laser diode driver with 5-decade range

A circuit is described which is capable of controlling the optical output of a laser diode over a 5-decade range under light feedback control. The circuit incorporates a 5-decade exponentially-controlled current source which is temperature compensated over its entire range. The driver operates from a -6-V supply.

Dependence of the device performance on the number of stages in quantum-cascade lasers

The cascading scheme is a characteristic feature of quantum cascade (QC) lasers. It implies that electrons above threshold generate one photon per active region they successively traverse. This paper presents a study of the cascading behavior as a function of the number N of stacked active regions. Experimental results are presented for devices with N=1, 3, 6, 12, 20, 30, 45, 60, and 75 active stages. The highest optical power and lowest threshold current density are obtained for laser devices with N as high as possible. However, the lowest threshold voltage and the lowest dissipated power at laser threshold are achieved for N=3 and N=22, respectively. We further present the highest power QC lasers so far, which, using N=75 stages, show in pulsed mode peak powers of 1.4, 1.1, and 0.54 W at 50 K, 200 K, and room temperature, respectively. Finally, we also demonstrate the first few-stage (N<10) QC lasers. These QC lasers show strongly reduced operating voltages. A threshold voltage around 1.5 V is achieved for N=3. This makes the lasers very well compliant with conventional laser diode drivers, which in turn will simplify their immediate use in systems and applications.

A compact MU-interface, 2.5-Gb/s optical transmitter module with LD-driver IC embedded in L-shaped wiring substrate

A 6.2-cc MU interface optical transmitter module has been developed in a compact packaging configuration that allows modules to be mounted side by side on a system board. The module employs an MU receptacle for optical output and miniature coaxial receptacles for electrical input. An L-shaped high-speed wiring substrate in a package cavity allows thermal isolation of a laser-diode driver IC (LD-DR) from the 1.55-/spl mu/m distributed feedback laser diode (DFB-LD) mounted on a thermoelectric (TE) cooler. A confocal two-aspheric-lens circuit is used for high-performance coupling of the DFB-LD to a dispersion-shifted fiber (DSF). A module using the proposed configuration has been evaluated at temperatures from 10-65/spl deg/C. Experiments with the module showed good electrical performance at a bit rate of 2.5 Gb/s, low power dissipation (less than 1.8 W; only 0.33 W for the LD-DR), and high optical coupling efficiency (over 50%).

Modeling the Geometry of the Laser Distance Sensor

The paper presents an analysis and design considerations for a non-contact distance sensor. The sensor operates on the triangulation principle and utilizes a low power laser beam as a source of light First, the paper describes the major components of the sensor and itS principles of operation. Also, additional electronic components, that are necessary for sensor operations, are briefly presented. These include a laser diode driver and a conditioning circuit for a position sensitive detector (PSD). Next, a model of the geometry for the distance sensing device is presented. Analysis of the sensor model results in a detailed description of the effects of the sensor's geometrical parameters on the performance of the sensor. In particular, non-linearity of its characteristics is analyzed in detail, and some design hints on how to avoid it are presented. Furthermore, major trade-offs, which must be considered while selecting design parameters of the laser sensing device, are described. Finally, the paper gives examples of possible applications of a non-contact laser distance sensor.

3.3 V, 50 Mbit/s one-chip Si-bipolar transceiverLSIfor optical burst-mode communications

A 3.3 V, 50 Mbit/s, one-chip transceiver LSI fabricated by a 4 GHz Si-bipolar process includes an adjustment-free instantaneous response receiver and a laser-diode (LD) driver to build a low-cost optical interface module for FTTH systems. The LSI, assembled with a conventional 0.8 A/W photodiode and 0.2 W/A LD, has an input optical receiver range of –37.8 to –17.0 dBm and an optical average output power of +6 dBm.

High-speed optoelectronic hybrid-integrated transmitter module using a planar lightwave circuit (PLC) platform

High-speed optoelectronic hybrid-integrated transmitter module has been developed using a silica-based planar lightwave circuit (PLC) platform on which a laser diode (LD) array and a two-channel LD driver IC were integrated. Heat absorption through a highly thermal conductive silicon terrace kept the average output power constant to within 5% during IC operation. Bit-error-rate (BER) measurement showed that this module operated successfully with a 9-Gb/s nonreturn-to-zero (NRZ) signal. This indicates that the PLC platform does not have any adverse effect on the frequency bandwidth of the integrated chips. This approach, using the PLC platform for integrating optoelectronic devices and electronic ICs, will lead to the development of a high-speed optical multichip module for optical signal processing.

High power laser diode driver based on power converter technology

This paper describes the design of a high speed semiconductor laser diode driver designed for driving 500 mW to 1.5 W diodes at full optical power modulation up to frequencies of 10 MHz. The duty cycle of the modulation may be varied. A switching power-converter based current source allows a higher power delivery efficiency to the diode than in previous designs, allowing for a more modest power supply and dissipation requirements. A dynamic ripple cancellation circuit reduces the power converter output current ripple to less than 1% of full-scale current. The circuit is capable of delivering up to 2.5 A to a laser load, with a 10-90% switching risetime from laser threshold to full on of less than 20 ns.

GaAs HIGH SPEED DEVICES AND CIRCUITS

This paper presents the R&amp;D of GaAs-based high speed devices and circuits at the Hebei Semiconductor Research Institute (HSRI) in China. It is concerned with low noise and medium power GaAs-MESFET MMIC and monolithic laser diode driver and preamplifier for 2.4 Gb/s fiber communication application, GaAs-based high speed digital circuits like single and dual modulus frequency divider, digital/analog convertor, shift register, HEMT and HBT integrated circuits.