Radio-Frequency Characteristics of Ultraviolet Optical Links

1
Radio-Frequency Characteristics of Ultraviolet
Optical Links
J. Deng, S. Halder, and J. C. M. Hwang, Lehigh
University A. Osinsky, SVT Associates H.
Seigneur, W. V. Schoenfeld, and L. Chernyak,
University of Central Florida
2
Outline

• Introduction
• Light-emitter diode (LED) characteristics
• Photo-detector (PD) characteristics
• LED-PD link DC characteristics
• LED-PD link RF characteristics
• Conclusion

3
Non-Line-of-Sight Covert Links
4
Current UV Links
Mercury lamp photo-multiplier tube bulky,
inefficient and expensive
5
Proposed UV Links
300µm
100µm
LED
PD1
GaN light-emitting diode photo-detector diode
compact, efficient, low cost
5µm
PD2
6
LED Emission Spectra
I (mA) 100 80 60 40 20
7
PD DC Characteristics
Dark Current
Photo Response
Comparable between () PD1 (?) PD2
8
Distributive R-C Effect
(?) PD2 () PD1
Both (symbol) measurement and (curve) simulation
show larger dispersion in PD1
9
DC LED-PD Link
Comparable between () LED-PD1 (?) LED-PD2
10
Small-Signal LED-PD Link
(?) LED-PD2 more wide- band than () LED-PD1
11
Bias Dependence of LED-PD1 Link
Bandwidth and gain of LED-PD1 link increase with
reverse bias of PD1
LED-PD2 link bandwidth independent of PD2 bias
12
Bias Dependence of LED-PD2 Link

• Bandwidth of LED-PD2 link increases with LED
  current
• Bandwidth of LED-PD1 link independent of LED
  current

13
Conclusion

• 370-nm link demonstrated at 60 MHz by using GaN
  LED and photo-detector
• Link bandwidth is orders-of-magnitude higher than
  that achieved by using lamp and tube
• Link bandwidth limited by LED instead of
  photo-detector
• Bandwidth improvement of solar-blind (lt280nm) LED
  in progress

14
Acknowledgment

• LED supplied by Tekcore Co., Taiwan
• Research sponsored in part by the U.S. Army
  Research Laboratory and was accomplished under
  Cooperative Agreement Number W911NF-06-2-0020.
  The views and conclusions contained in this
  presentation are those of the authors and should
  not be interpreted as representing the official
  policies, either expressed or implied, of the
  Army Research Laboratory or the U.S. Government.