We present a smart pixel with surface-normal optical input and output beams using a vertical cavity surface-emitting laser. In its present nonoptimized hybrid version, the smart pixel exhibits opto-optical switching with a contrast of 35 dB, an optical gain of 55 dB and a 3 dB bandwidth of 90 MHz. The optical switching energy is 715 fJ. NOR, and NAND logic operations at 4 Mbit/s with a fan-out of 5 are also demonstrated.
We present a novel smart pixel composed of an optoelectronic threshold switch with gain and a vertical cavity surfaceemiuing laser (VCSEL). In this smart pixel two surface-normal input optical beams control an output optical beam emitted by the VCSEL. In its present hybrid version the VCSEL-based smart pixel is capable of opto-optical switching with an output contrast ratio in excess of 30 dB at an optical output power of about 1.5 mW. For quasi-stationary operation we achieve an optical gain of up to 3 x iO. We also report drastic improvements on the switching dynamics. Operating the receiver with an optical input power of 130 pW we achieve bitrates of up to 160 Mbitls and an optical gain of 1 1, while optical inputs of 410 iW result in a maximum bitrate of 400 Mbit/s and an optical gain of 3.6. The minimum input optical energy required for switching is 765 IJ, the AC output contrast ratio is 9 dB. Optically performed NAND and NOR logic operations are demonstrated at 40 Mbitls with a fan-out of 7.6. We further show that the functionality of this smart pixel can easily be extended to electric read-out of input optical data and to direct electric control of the VCSEL within the smart pixel configuration. In particular, we demonstrate conversion of electric input to optical output data at 1 Gbitls.
R Windhch, B. Dulta, aud P. tkremms IMEC, K S~~I~K C~~S , 3001 ~~~~e~, udpiUmIn this &?per we present a contiqt for Ihc mooolithic integration ofs special photoconduclivc receiver with P It&> diicicncy LED, lcadingto asimplc bul powerful smadplxrl deeviw.The receiver o f this smm pixel has a l d y been presented elsewbm [I] I1 coiisists of B n-i-p rcfercncc dwdc in $cries with a specially designed photnanductive n-i-p detector (cf. Fig. I). A cammm bias volmge U,. is applied a s m s both diodcs. Since the photoconductive &lector i s basically B combination ofa n~i-p pholodiodc and a back-gated Aeldzffcct tmnsisI0r. the nchanncl an lop ortho dokctor can bo deplctcd by applying a sufficiently neptive bias acms the pn-iwction. Undcr illumination ( M x 5 nm) the common bias vollagc U,. will dmp amos lhnt diode which r-i~cs kss optid powcc. 'Thus, the outpul currenl of the u w e i can he controlled by lhc illvminatim of t11c two input diodes. In the on-sutc thc output current of the receiver 6 suficienlly hi& to directly drive an actwe transmitter. Thls h a been demonslmrcd in [I] using a venical cavity laser (VCSSL). Unfanuwtcly, the VCSEL requires B complicated design, mhking thc 8monolilhic inlcgraclon wllh the reCCiYCr d!llicull. Thc rccently dcvclOped non-resonant cavity LEDs (NRC-LEDs) [?I require a rt.lativcly simplc fabrication pmces. Thus Ihcy arc much kltcr suited for monolithic inlegrvlion with our ,Cc%c,rcr. The NRC-LED is depicMd on lhc right pml of Fig. 1. The milin inlprovcmrnl~ over a nom1 LED srmcture are thc mar mirror, tht f~xtllring of the rurfacc. and a cumnt apeflure similar to those u r d ~n VCSEL dcrigns. Due lo thee impnvomenlr thc extemal quantum cficicncy rises from about 2 % in normal LED stmctums m over 40 X in NRC-LRDs (for details sec 121). This, we helleve Ulatthe~e NRC-LElh arc w d s l u M for nmny mcdium p w e r qplicufions. Furhemore, lhe simple structure o f a NRC-LEU allows for easy monolithic intcgrdlioll wllh other componenll and also for large arrays o f dcviccs In ow present Arsi implcm~nlaiion ofthe concept the a-i-p structure for the m i v e r is smcbd on Dp ofthc LED ~tw1w.z (cf. Fig. 2). All dcvicrs use thc sunc playcr. The tots1 height ofthe dnricea is 2.s ~m and does not came any problems far lithapaphic processes. Good DC performance of the smvrtpixcl devices ha b e n demonslr&td AC mca.surmCOtS are in ProperS. 1h ~onduion, mon~lithic integration of a photocanductwe receiver and il NRC-LED has been aClllCVCd 09.15 CWD3 0-7803-6319-1/00/$10.00@)2000 IEEE
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