Pulsed Laser Diode Test System
Contents
1. Simplifies laser diode LIV testing prior to packaging or active temperature control Integrated solution for in process LIV production testing of laser diodes at the chip or bar level Sweep can be programmed to stop on optical power limit Combines high accuracy source and measure capabilities for pulsed and DC testing Synchronized DSP based measurement channels ensure highly accurate light intensity and voltage measurements Programmable pulse on time from 500ns to 5ms up to 4 duty cycle Pulse capability up to 5A DC capability up to 1A 14 bit measurement accuracy on three measurement channels V front photodiode back photodiode Measurement algorithm increases the pulse measurement s signal to noise ratio Up to 1000 point sweep stored in buffer memory eliminates GPIB traffic during test increasing throughput Digital I O binning and handling operations IEEE 488 and RS 232 interfaces 1 888 KEITHLEY us only 2620 PULSED LASER DIODE TEST SYSTEM r aa la TECT Ta TECTO eQ o RANGE um on jac Gu me en E em on mo C5 Enten Remote Electrical Test Head included ulsed Laser Diode Test System The Model 2520 Pulsed Laser Diode Test System is an integrated synchronized system for testing laser diodes early in the manufacturing process when proper temperature control cannot be easily achieved The Model 2520 provides all sourcing and measurement2. ACCESSORIES AVAILABLE The mainframe and remote test head architecture of the Model 2520 is designed to enhance pulsed measurement accuracy even at the sub microsecond level The remote test head ensures the meas 2520INT 1 GE Integrating Sphere 1 inch with Germanium j ea TR urement circuitry is located near the DUT mounted on the fixture minimizing cable effects As the 1 cB O O oO wn S z N wo g O oO a fox 5 oO de F B Detector 7007 1 Double Shielded GPIB Cable 1m 3 3 ft schematic in Figure 1 shows traditional semi custom systems typically employed in the past require 7007 2 Double Shielded GPIB Cable 2m 6 6 ft significant integration The architecture of the Model 2520 Figure 2 offers a far more compact and KPCI 488LPA IEEE 488 Interface Controller for the PCI Bus r eady to use solution JSB 4 488 USB to J r PNT BO ape eee ee iene GET Adapter ens High Speed Pulse and Measure to Minimize Thermal Effects SERVICES AVAILABLE The Model 2520 can accurately source and measure pulses as short as 500 nanoseconds to minimize unwanted thermal effects during LIV testing Users can program the pulse width from 500ns to 5ms date of shipment and pulse off time from 20s to 500ms There is a software duty cycle limit of 4 for currents higher 2520 3Y DATA 3 2540 1 compliant calibrations within 3 years than 1A To ensure greater accuracy the instrument provides pulse width
3. 1year 23 C 5 C 0 6 0 515 2 Ify Duty Cycle I exceeds 0 2 accuracy specifications must be derated with an additional error term as follows Full Pulse 500mA Range 0 1 rdg VD I 0 5 0 51 5A Range 0 3 rdg YD I 0 4 0 505 where I current setting Expanded Pulse Top Current D duty cycle 0 3 fo fo 0 5 A This derating must also be applied for a period equal to the time that VD Iwas 20 2 0 2 0 495 3 Not including overshoot and setting time 4 Pulse mode only 0 1 0 49 5 Output 500mA DC on 500mA range and 1A DC on 5A range 6 Refer to Model 2520 Service Manual for test setup of current accuracy o 0 485 7 Figures 1 and 2 are typical pulse outputs into resistive loads 25 8 Typical 9 Per ANSI IEEE Std 181 1977 10 Per ANSI IEEE Std 181 1977 10 to 90 11 DC accuracy 700mV output terminal 0 2Q typical output impedance Figure 1 12 At DC 104s measurement pulse width filter off 13 Standard deviation of 10 000 readings with 10s pulse width filter off with I source set to 0A DC 14 The A D converter has 14 bit resolution The useful resolution is improved by reading averaging The useful resolution is Pulse Waveform Flatness 5A into 2 Ohms Range 1 Useful Resolution 14 5 06 2 J Pulse Width ns 400ns 100ns Full Pulse Averaging Filter Setting 3 04 15 Excluding total programmed Pulse ON time Pulse OFF time 5 02 16 Front panel off calc off filter off duty cycl
4. even eliminate time consuming GPIB traffic during a test sequence The Buffer Memory can store up to 1000 points of measurement data during the test sweep The Trigger Link combines six independent soft ware selectable trigger lines on a single connector for simple direct control over all instruments in a system This interface allows the Model 2520 to operate autonomously following an input trigger The Model 2520 can be programmed to output a trigger to a compatible OSA or wavelength meter several nanoseconds prior to outputting a programmed drive current value to initiate spectral measurements Accessories and Options The Model 2520 comes with all the interconnecting cables required for the main instrument and the remote test head Production test practices vary widely automated vs semi automated vs manual so the cable assemblies from the remote test head to the DUT can vary significantly To accommo date these differing requirements Keithley has developed the Model 2520 RTH to DUT Cable Configuration Guide to help customers determine the proper cable assemblies to use to connect the remote test head RTH to the DUT Interface Options The Model 2520 provides standard IEEE 488 and RS 232 interfaces to speed and simplify system integration and control A built in digital I O interface can be used to simplify external handler control and binning operations Additional LIV Test Solutions For production testing laser diodes after t
5. laser diode manufacturers Note that the use of discrete test measure capabilities in a single half rack instrument with remote Lu ie a e 1 888 KEITHLEY U S only KEITH LEY www keithley com A GREATER MEASURE OF CONFIDENCE 2520 physics of the connections to the device Keithley s optoelectronics applica tions engineers have addressed these issues by studying and documenting the optimum cable configuration to enhance measurement accuracy with extremely fast pulses Figure 3 illustrates the results of a typical pulse LIV sweep test with the Model 2520 In this test a 100 point pulsed LIV sweep using a lus pulse width at 1 duty cycle was completed in just 110ms including data transfer time several orders of magnitude faster than existing semi custom test systems ESD Protection A laser diode s material make up design and small size make it extremely sensitive to temperature increases and electrostatic discharges ESDs To prevent damage prior to the start of the test and after test completion the Model 2520 shorts the DUT to prevent transients from destroying the device The instrument s 500 nanosecond pulse and measure test cycle minimizes device heating during test especially when a short duty cycle is used Test Sequencing and Optimization Up to five user definable test setups can be stored in the Model 2520 for easy recall The Model 2520 s built in Buffer Memory and Trigger Link interface can reduce or
6. programming resolution of purchase levels of 10us off time and 100ns on time Not available in all countries 2520 3Y EW 1 year factory warranty extended to 3 years from Prior to the introduction of the Model 2520 test instrument limitations often placed barriers on test performance However with the Model 2520 the limiting factor is not the test instrument but the components increases the integration and programming effort while test head to provide maximum flexibility and test throughput severely limiting the flexibility of the test system Model 2520 i Remote Test Head Nigt Spoed ci High Speed urrent to i 3 of io See Converter Front i Converter Facet HE J Detector ni Voltage Measure 2520INT 1 ii H Sequencing i Ba i High Speed i Sequencing igh Speed ni and Signal 4 Pulse Laser Diode l i High Spee ni i Analysis amn Source A Chip or Bar i yg Multi Channel pulse Cae _ Computer SeeecoRe DSP Digitizer P T T t Rear i T A P Facet T Detector Parallel Custom Bus ht High Speed pi High Speed N curent to ZA Current to W loltage H ba Voltage we Converter 3 Tt Converter zZ ie 8 Figure 1 This schematic reflects the current testing practices of Figure 2 The Model 2520 integrates synchronization source and rfl major
7. to production bottlenecks Higher Resolution for Higher Yields To achieve the required signal to noise ratio traditional chip and bar level LIV testing solu tions have required the use of boxcar averagers or test system control software modifications to allow averaging several pulsed measurements The resolution of these measurements is criti cal for the kink test and threshold current calculations With earlier test system designs particularly when performing the kink test low resolution and poor linearity of the analog digitizer made it extremely difficult to discrimi nate between noise in the measurement and an actual device kink The Model 2520 s unique DSP based measurement approach automatically A GREATER MEASURE OF APPLICATIONS Production testing of e Telecommunication laser diodes e Optical storage read write head laser diodes e Vertical Cavity Surface Emitting Lasers VCSELs Thermal impedance e Junction temperature response CONFIDENCE 2 Lu n zZ e U Lu l Lu e a e Pulsed Laser Diode Test System identifies the settled region of the pulsed waveforms measured This means the Model 2520 stores only that portion of the pulse that is flat and contains meaningful data All measurements made in the flat portion of the pulse are averaged to improve the Signal to Noise ratio still further If greater resolution is required the Model 2520 can be progr
8. ammed to perform several pulse and measure cycles at the same pulse amplitude By making it possible to conduct more thorough testing at the bar or chip level the Model 2520 also eliminates the wasted time and costs associated with assem 2520 KIT1 bling then scrapping modules with non compliant diodes Pulsed Laser Diode Measurement Kit Simple One Box Test Solution includes 2520 2520INT The Model 2520 offers three channels of source and measurement circuitry All three channels are and 3 ft triax cable controlled by a single digital signal processor DSP which ensures tight synchronization of the sourcing and measuring functions The laser diode drive channel provides a current source coupled with voltage measurement capability Each of the two photodetector channels supplies an adjustable User s Manual Quick Reference voltage bias and voltage compliance in addition to current measurement capability These three Guide Triax Cables 2 channels provide all the source and measure capabilities needed for full LIV characterization of laser BNC 10Q Coaxial Cables 4 diodes prior to integration into temperature controlled modules By eliminating the need for GPIB commands to perform test sweeps with multiple separate instruments the Model 2520 s integrated sourcing and measurement allows a significant improvement in throughput 2520 Pulsed Laser Diode Test System with Remote Test Head Remote Test Head Maximizes Signal to Noise Ratio
9. cal Accuracy typical Programming Electrical Accuracy Range Resolution Resolution rdg mA 3 1kHz 20MHz Range Resolution Resolution rdg mA 0 500 mA 10 uA 8 uA 0 2 0 45 70 uA 0 15 mA 1yA 7 nA typ 0 2 0 45 0 1 0 A DC 0 5 0 A Pulse 100 uA 80 uA 0 2 45 800 uA 0 150 mA 10 uA 70 nA typ 0 2 45 TEMPERATURE COEFFICIENT 0 18 C amp 28 50 C 0 15 x accuracy specification C Pulse PULSE ON TIME 500ns to 5ms 100ns programming resolution Setting and Pulse Overshoot Rise Fall Time 8 9 10 PULSE OFF TIME 20us to 500ms 10us programming resolution Range Load Mode Max 89 Typical Max PULSE DUTY CYCLE 21 0 to 99 6 for lt 1 0A 0 to 4 for gt 1 0A ii a i lt a mac A i ion VOLTAGE COMPLIANCE 3V to 10V 10mV programming resolution 500 mA 102 Watt Sas 01 ils ISNS POLARITY 1 quadrant source polarity reversal available through internal relay inversion 5 00 A 15Q 1 Watt Fast 1 0 100 ns 130 ns OUTPUT OFF lt 200mQ short across laser diode measured at Remote Test Head connector 5 00 A 15Q 1 Watt Slow 0 1 lus 1 3 us LASER DIODE VOLTAGE MEASURE SPECIFICATIONS GENERAL Minimum Accuracy RMS Noise Range Resolution rdg volts 12 typical DC eas VOLTAGE User may float common ground up to 10VDC from chassis ground 3007 0 33 mV 03 6 5 mV 60 uV COMMON MODE ISOLATION gt 10 Q _1000v 66 mV HF BVO OVERRANGE 105 of range on all measurements and voltage co
10. capabilities needed for pulsed and continuous LIV light current voltage testing of laser diodes in one compact half rack instrument The tight synchronization of source and measure capabilities ensures high measurement accuracy even when testing with pulse widths as short as 500ns LIV Test Capability The Model 2520 can perform pulsed LIV testing up to 5A and continuous LIV testing up to 1A Its pulsed testing capability makes it suitable for testing a broad range of laser diodes including the pump laser designs for Raman amplifiers The instrument s ability to perform both DC and pulsed LIV sweeps on the same device simplifies analyzing the impact of thermal transients on the LIV characteristics of the laser diode Maximize Throughput and Eliminate Production Bottlenecks By working in cooperation with leading laser diode manufacturers Keithley designed the Model 2520 specifically to enhance chip and bar level test stand yield and throughput Its inte grated design ease of use high speed and high accuracy provides a complete solution to help laser diode manufacturers meet their production schedules Producers of laser diodes face con stant pressure to increase test throughput and optimize return on investment for their capital equipment used in production testing Until recently these producers were forced to use relatively slow and cumbersome test stands for testing laser diodes at the chip and bar level which often led
11. e lt 10 binary communications Current Expanded Pulse Top Current 17 Returning 1 voltage and 2 current measurements for each source point A pepan ee 5 A 18 Sweep mode 19 Valid for both continuous pulse and sweep modes 20 Shown is the Power Distribution based on current settings 21 Timing Cycle P pw pd 4 max Model 2520 specifications 10 15 Time us Figure 2 Pulse Output Trigger Output Relationship igger onan 2 1 00E 06 5 00E 07 0 00E 00 5 00E 07 1 00E 06 1 50E 06 Time Figure 3 n Lu n S zZ e U Lu l Lu ie a e 1 888 KEITHLEY v s only KEITHLEY www keithley com A GREATER MEASURE OF CONFIDENCE
12. hey have been packaged in temperature controlled modules Keithley offers the Laser Diode LIV Test System with increased 28 bit core measurement resolution allowing for more detailed characterization This flexible system combines all the DC measurement capabilities required to test these modules with tight temper ature control over the DUT in a modular instrument package Configured from proven Keithley instrumentation the basic configuration can be easily modified to add new measurement functions as new testing needs evolve 1 888 KEITHLEY U S only www keithley com Pulsed Laser Diode Test System Figure 3 This plot illustrates the Model 2520 s pulsed LIV sweep capabil ity The sweep was programmed from 0 to 100mA in 1mA steps Pulse width was programmed at 1p s at 1 duty cycle providing for a complete sweep in just 10ms excluding data transfer time Figure 4 Model 2520 Remote Test Head KEITHLEY GREATER MEASURE OF CONFIDENCE n oO 2 2 wT oO wn 5S o z wn oO g gej oO Aa a 5 f 1S oO oe 2 B OPTOELECTRONICS TEST Model 2520 specifications 7a Lud 7a U zZ e 1 Lu d Lu e 5 e 2520 Pulsed Laser Diode Test System LASER DIODE PULSE OR DC CURRENT SOURCE SPECIFICATIONS DRIVE CURRENT OFF CURRENT Approx RMS Noise Approx Source Programming Electri
13. mpliance TEMPERATURE COEFFICIENT 0 18 C amp 28 50 C 0 15 x accuracy specification C SOURCE OUTPUT MODES MAX LEAD RESOLUTION 100Q for rated accuracy 2 se nae I ixed Pulse Leve INPUT IMPEDANCE 2MQ differential IMQ from each input to common DC Sweep linear log and list Input bias current 7 5uA max Pulse Sweep linear log and list Continuous Pulse continuous low jitter PHOTODIODE VOLTAGE BIAS SOURCE SPECIFICATIONS each PROGRAMMABILITY IEEE 488 SCPI 1995 0 RS 232 5 user definable power up states plus channel factory default and RST RANGE 0 to 20VDC DIGITAL INTERFACE PROGRAMMING RESOLUTION 10mV Safety Interlock External mechanical contact connector and removable key switch ACCURACY 1 50mV Aux Supply 5V 300mA supply CURRENT 160mA max with V Bias shorted to I Measure Digital I O 2 trigger input 4 TTL Relay Drive outputs 33V 500mA max diode RMS NOISE 1kHz to 5MHz ImV typical clamped Trigger Link 6 programmable trigger input outputs PHOTODIODE CURRENT MEASURE SPECIFICATIONS Pulse Trigger Out BNC 5V 50Q output impedance output trigger corresponding to each channel current source pulse pulse to trigger delay lt 100ns See Figure 3 MAINS INPUT 100V to 240V rms 50 60Hz 140VA R pentane i DC input H dacutay giz j aape EMC Conforms to European Union Directive 89 336 EEC EN61326 1 Range _ Resolution _ Impedance rdg current typical _ SAFETY Conforms to Eu
14. ropean Union Directive 73 23 EEC EN61010 1 CAT 1 1O OUA 0 7 4A 108 03k 20 uA 90 nA VIBRATION MIL PRE 28800F Class 3 Random SE 14uA lt 62 0 3 65 mA 180 nA WARM UP 1 hour to rated accuracy 50 00 DIMENSIONS WEIGHT RN 3 4 uA lt 30 0 3 90 uA 420 nA Main Chassis bench configuration with handle amp feet 105mm high x 238mm wide x 416mm deep 4 in x 9 in X 16 in 2 67kg 5 90 Ibs 100 00 mA 6 8 uA lt 25Q 03 175 pA 840 nA PANN CCED RPA AIS ODS TO FG Mh Mh Mm Mm em Fh Th Remote Test Head 95mm high x 178mm deep with interlock key installed x 216mm wide 3 in x 7 in x 8 in 1 23kg 2 70 lbs ENVIRONMENT Operating 0 50 C 70 R H up to 35 C Derate 3 R H C 35 50 C with no damage although calibration may be affected Storage 25 to 65 C TEMPERATURE COEFFICIENT 0 18 C amp 28 50 C 0 15 x accuracy specification C INPUT PROTECTION The input is protected against shorting to the associated channel s internal bias supply The input is protected for shorts to external supplies up to 20V for up to 1 second SYSTEM SPEEDS READING RATES ms 5 16 Number of To To Source Points Memory GPIB 1 5 3 6 8 108 25 18 1008 48 120 10008 431 1170 1 888 KEITHLEY U S only KEITH LEY www keithley com A GREATER MEASURE OF CONFIDENCE 2520 Pulsed Laser Diode Test System NOTES Pulse Waveform Flatness 500mA into 20 Ohms Ses 1
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