Radiation hardness of the 1550 nm edge emitting laser for the optical links of the CDF silicon tracker S. Hou 15-Jun-2004

Optical links at CDF Dense Optical Interface Module (DOIM) Byte-wide parallel optical link 8-bits + clock 53 Mbyte/sec, BER  Laser transmitter Edge-emitting diode array Ribbon fiber cable (22 m) multi-mode Ge doped PIN receiver

DOIM modules Laser diode transmitters on Port Cards inside detector Total 570 transmitters 128 Port Cards, PIN diode receivers on FTM board out in VME crates

Laser transmitter InGaAs/InP Edge-emitting laser diode array 1550 nm wavelength 12-ch diode array, 250  m pitch Bare die power,  1 Custom made by Chunghwa Telecom biCMOS ASIC driver bipolar transistors, AMS 0.8  m process Inputs: Diff. ECL or LVDS differential  100 mV Enable by TTL low Output light: adjustable by ~2mA/0.1V At V cc -V LD =3V, 20mA/ch

Laser transmitter assembly Die-bond / Wire bond laser-diode array on BeO submount driver chip on substrate fibers on V-groove Alignment fibers to laser emitting facets Ligut ouput at fiber end: 200 ~ 800  W/ch

Receiver module Die-bond / Wire bond PIN-diode array on Al 2 O 3 submount driver chip on substrate fibers on V-groove to PIN diodes InGaAs/InP PIN diode 12-ch array, 1550 nm by TL, Chunghwa Telecom. Operation condition : light on: 50 ~ 800  W light off:  10  W  1.1 W/module Outputs : Nine independent diff. ECL

Laser transmitter characteristics Inputs: ECL or LVDS signal TTL-enable Light by O/E probe Input ECL TTL enable

Laser transmitter current balance Constant Current through LDA or dummy 50  max.  I ~ 7mA/module (<4%) Prevent wirebond resonance Current probe O/E light TTL enable Broken bond observed for 2 mm AlSi bond at 15 kHz

Laser diode: L-I-V Laser light at I,V and Temperature I-V approximately linear Duty cycle stable output to input 50% Linear to temperature Temp ( o C)

Rad-hard requirement at CDF Transmitters on Portcard at r= 15 cm 450 pb -1 delivered to CDF TLD (thermoluminescence Dosimeters) measurement ~ 15 rad / pb -1 (5.8E8 MIPs/cm 2 ) TLD radiaition measurement in CDF tracking volume ( Portcard position CDF luminosity

Bulk damage to laser light yield Laser transmitter specification : 200 krad tolerance Bulk damage is dominant Ratio of light drop is consistent for a module, indep. of light power Degradation  10% for 200 krad INER proton 30 MeV DC mode 200 krad=1.1E12/cm 2 (8E12 /cm 2 1MeV n) UC Davis proton 63.3 MeV AC mode on PortCard 200 krad=1.8E12/cm 2 (12E12 /cm 2 1MeV n)

INER 30 MeV proton Irradiation transmitter in DC mode online monitoring light level & temp. total 1.8 Mrad, 1E13/cm 2 (30 MeV p) 24 hrs annealing with 10% recovery irradiated in 12 cycles, 1 min beam-on 4 min off ripple due to temp. rise at beam-on by 1 o C to 25 o C

ECL 25MHz inputs O/E probing for biCMOS driver wave form IUCF 200 MeV proton Irradiation Before irradiation at fluence=3.0x10 13 (1.4 Mrad GaAs 1.8 Mrad Si)

Irradiation study : AC,DC modes AC to DC mode Cumulative fluence: 6.8, 13.6 E12/cm2 200 MeV p ( 48, 97 E12/cm2 1MeV n 320, 640 krad ) AC mode in 3 flux rate 3.4, 11.5, 29.2 E9/cm 2 sec Cumulative fluence: 4.3, 12.8, 30 E12/cm 2 200MeV p ( 31, 91, 214 E12/cm 2 1MeV n 200, 600, 1400 krad )

 8hrs annealing IUCF 200 MeV proton DC mode, 3 flux rate, 4.9, 7.2, 13.2 E9/cm 2 sec 8 hrs annealing Cumulative fluence: 1.7, 5.1, 11.9 E12/cm MeV p ( 12, 36, 85 E12/cm 2 1 MeV n 80, 240, 560 krad ) Irradiation study: flux rate, annealing

Summary CDF optical links are in stable service daily maintenance are temperature, ECL related Radiation tolerance is sufficient for the Run II program irradiation tests  laser light degradation is less than 10% at 200 krad no damage observed on driver chip wave form