From - Fri Nov 22 15:59:45 1996 Xref: nsc sci.optics:23472 Path: nsc!voder!nntp-hub3.barrnet.net!su-news-hub1.bbnplanet.com!news.bbnplanet.com!cam-news-hub1.bbnplanet.com!howland.erols.net!vixen.cso.uiuc.edu!uwm.edu!src.honeywell.com!not-for-mail From: wilson_mark@htc.honeywell.com (Mark Wilson) Newsgroups: sci.optics Subject: Re: Pulsing of Laser Diode? Date: 20 Nov 1996 09:45:00 CST Organization: Honeywell Technology Center Lines: 47 Message-ID: <56v91s$6f1@moon.htc.honeywell.com> References: <56o0hb$8ju@herald.concentric.net> NNTP-Posting-Host: markw.htc.honeywell.com X-Newsreader: WinVN 0.90.5 I have personally used this method to modulate laser diodes up to 1.3 GHz. It is safe as long as your input voltage does not exceed a volt or so. You can use diode clamping to eliminate the over voltage issue. If you wish to have an occational pulse of ligh (as requested in the first post) this will work. If you wish to modulate the laser with a sine wave or use Manchester encoded data, this method will work. However, if you wish to use general NRZ encoded data where you can have long strings of 1111111's or 000000's in a row, this method will not work. By using the low capacitance AC input, it acts as a current limiter. If you replace the 500 pF capacitor with a .1 uF you easily damage the laser diode. Yes it is possible to still blow out a laser using the circuit I described, but you always have to be carefull and know what you are doing. In article , sam@stdavids.picker.com (Sam Goldwasser) says: > >I may be misunderstanding the circuit details but this sounds like a good >way to blow the laserdiode. Maximum current is critical and must not be >exceeded even for a microsecond. > >--- sam > >In article <56sjv2$dde@moon.htc.honeywell.com> wilson_mark@htc.honeywell.com (Mark Wilson) writes: > > Yes this can be easily done. Try using a DC driver such as the Sharp IR3C07 > to DC bias a 630 nm laser diode (as close as you can get to 600 at this time) > slightly above its threshold current. Use a small inductor (100uH) to connect to > the laser. At that same point where the inductor connects to the laser, also > connect up a high Q ceramic capacitor of 500 to 1000 pF (actual values may need > to be adjusted). Input an electrical pulse with the attributes you mentioned > and then adjust the bias current, and capacitance till you obtain an optical > pulse with the required characteristics. Use a reversed biased photo diode with > a tranimpedence amplifier to view pulse shape (not the internal power stabilization > photodiode inside the laser). > > > In article <56o0hb$8ju@herald.concentric.net>, rsansbury says: > > > >Can Laser diodes be turned rapidly on and off by changing the applied > >voltage rapidly? For example could one produce 50nsec 1mW light pulses > >with say 10nsec rise and fall times at some visible frequency eg 600nm > >followed by 150nanoseconds off etc over several seconds? And could one > >similarly turn on and off a photodiode driven by the same clock > >oscillator at synchronized time intervals? > >Ralph Sansbury rns@concentric.net > >