THE WORLD'S FASTEST ELECTRONIC SWITCH - Do-it-Yourself Frequency Calibration

Sep 29, 2026

Newsletter content covering two electronics-related features: a discussion of a fastest electronic switch developed at Bell Laboratories using mode-locked Nd:glass laser pulses focused on undoped silicon, including its measured 10 picosecond switching time and the underlying optical-pulse induced photoconductivity and carrier geometry effects. A second feature explains a practical do-it-yourself method for frequency calibration using a color TV to tune into rubidium-controlled atomic oscillator signals broadcast as color-burst references from ABC, CBS, and NBC, with simple comparators and a 358 Frequency Measurement Computer option plus accuracy expectations and calibration traceability to NBS.

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THE WORLD'S FASTEST ELECTRONIC SWITCH

DO-IT-YOURSELF FREQUENCY CALIBRATION

Color TV atomic oscillator calibration system

Comparator and 358 Frequency Measurement Computer

NEWSLETTER Report to Senior Electronics Engineers &Managers May 1975Volume 95,Number 5 # THE WORLD'S FASTEST ELECTRONIC SWI TCH Do you ever get the feeling that things are going fasterand faster?If so,then join the crowd:it's a'sign of thetimes.And among the new signposts evident along the routeof scientific progress is what is probably the fastestelectronic switch ever devised. David Auston,a research scientist at Be11 Laboratories,developed the new device and has measured its switchingtime to be as short as 10 picoseconds."This is 10 to 100times faster than conventional semiconductor switches,such as transistors,and the limiting speed has not beenreached,"Auston says. This line of research is not simply to go faster andbreak records;it is significant because it should providehigh1y-accurate instrument calibration,such as forhigh-speed oscilloscopes,as wel1 as greater understandingof the photoelectric effect on these small time scales. Auston explained to Electro-Technology that light pulsesfrom a mode-1ocked Nd:glass laser are focused onto pureundoped silicon;these beams cause the semiconductor toact like a switch for manipulating electrical signals. "We generate optical pulses of about a few times 10-12 secwith the laser,"Auston explains."And we are able to usethe photoconductivity arising from the pulse absorption todo fast switching."(Josephson junctions and fast diodesare also thought to have switching speeds up to 1 psec,but as yet these haven't been used in complete systems ofgenerating and measuring electrical signals.) In the Bell Labs'system,an optical pulse in the greenregion of the spectrum produces quantities of electronsand holes of such densities(10-20/cc)that the silicon,originally exhibiting high electrical resistivity,becomesnear1y metallic,having conductivity only a factor of 10 Copyright@1975 by Industrial Research,222 S.RiversidePlaza,Chicago,I11.60606.Reproduction prohibited withoutpermission. less than copper.But this conductivity is long-lived(a few nsec to a few μsec),so a second 1aser pulse isdirected,this time in the IR region and at a differentlocation on the crystal. This second pulse produces carriers in a different geometrythan the first,and the net effect is to terminate theelectrical properties—an "off"switch. "We are able to make linear gates,pulse generators,andso forth,"Auston says."But to measure the extremely fastswitching times,we also had to design special instrumentsusing these very same materials." To do this,the pulse generator,producing pulses of 50-psecduration and 50 to 100 V in amplitude was connected to alinear gate with a comparable window(15 psec)to measurethe pulse generated."We expect to get down to 1 psec withouttoo much trouble,"Auston states."And we can handle quitehigh voltages as we11." Initial applications wil1 probably be limited to laboratorystudies of semiconductor materials and evaluating high-speedelectronic devices.Longer range uses,however,may includeshort-pulse microwave radar and transmission systems aswe11 as high-speed measuring instruments. # DO-IT-YOURSELF FREQUENCY CALIBRATION You can use a color TV to frequency-calibrate your1oscillators with an accuracy to a few parts in 10¹1,andyou can do it quickly and inexpensively.The National Bureauof Standards has developed a simple system that allowsanyone to"tune in"to the atomically-controlled oscillatorsignals from the three national television networks,andcalibrate their own instruments. The system is based on the fact that ABC,CBS,and NBCnetworks use rubidium-controlled oscillators to form thecolor-burst signals required for color TV.NBS monitorsthese signals,compares them with the NBS atomic frequencystandards,and publishes the average differences.As aresult,anyone with a color TV set has access to a numberof atomic oscillator signals and,with precise offset datafrom NBS,can make frequency calibrations that are directlytraceable to NBS. There are two types of instruments

FAQs

What switching speed did Bell Laboratories measure for the new electronic switch?

The device’s switching time was measured to be as short as 10 picoseconds.

Why does the silicon act like a switch in the described system?

Light pulses focused onto undoped silicon generate photoconductivity, turning the material nearly metallic, and a second pulse at a different location terminates the electrical properties to create an “off” state.

How can a color TV be used for do-it-yourself frequency calibration?

The method uses rubidium-controlled oscillator signals embedded in color-burst information from major TV networks, monitored against NBS atomic frequency standards; with published offset data, users can time color changes and adjust their oscillators accordingly.

Sep 29, 2026

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