radio-frequency characteristics of ultraviolet optical links
DESCRIPTION
Radio-Frequency Characteristics of Ultraviolet Optical Links. J. Deng , S. Halder, and J. C. M. Hwang, L ehigh University A. Osinsky, SVT Associates H. Seigneur, W. V. Schoenfeld, and L. Chernyak, University of Central Florida. Outline. Introduction - PowerPoint PPT PresentationTRANSCRIPT
Radio-Frequency Characteristics of
Ultraviolet Optical Links
J. Deng, S. Halder, and J. C. M. Hwang, Lehigh UniversityA. Osinsky, SVT Associates
H. Seigneur, W. V. Schoenfeld, and L. Chernyak, University of Central Florida
• Introduction• Light-emitter diode (LED)
characteristics• Photo-detector (PD)
characteristics• LED-PD link DC characteristics• LED-PD link RF characteristics• Conclusion
Outline
Non-Line-of-Sight Covert Links
Current UV Links
Mercury lamp + photo-multiplier tube= bulky, inefficient and expensive
Proposed UV Links
GaN light-emitting diode +photo-detector diode
= compact, efficient, low cost
5µm
PD2
100µm
PD1
300µm
LED
0
1
2
3
300 350 400 450
Wavelength (nm)
Em
issi
on
In
ten
sity
(a.
u.) I (mA)
100
80
60
40
20
LED Emission Spectra
PD DC Characteristics
-12
-8
-4
0
-6 -4 -2 0 2 4Bias (V)
Lo
g C
urr
ent
(A)
-12
-10
-8
-6
200 400 600 800
Wavelength (nm)
Lo
g C
urr
ent
(A)
Photo Response
Dark Current
Comparable between(■) PD1 & (▲) PD2
0
2
4
6
8
10 100 1000Frequency (MHz)
Cap
acit
ance
(p
F)
Rs+RL
R
C
Distributive R-C Effect
Both (symbol) measurement and (curve) simulation show larger dispersion in PD1
(▲) PD2
(■) PD1
0.0
0.4
0.8
1.2
1.6
0 20 40 60
LED Current (mA)
Det
ecto
r C
urr
ent
(μA
)DC LED-PD Link
Comparable between(■) LED-PD1 & (▲) LED-PD2
-15
-10
-5
0
5
0 20 40 60 80
Frequency (MHz)
No
rmal
ized
Po
ut
(dB
)
(▲) LED-PD2 more wide- band than (■) LED-PD1
Small-Signal LED-PD Link
20
25
30
0 5 10
Detector Bias (V)
Ban
dw
idth
(M
Hz)
0
4
8
12
No
rmal
ized
Gai
n (
dB
)
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
0
20
40
60
80
0 20 40 60
LED Current (mA)
Ban
dw
idth
(M
Hz)
-4
-2
0
2
No
rmal
ized
Gai
n (
dB
)
Bias Dependence of LED-PD2 Link
• Bandwidth of LED-PD2 link increases with LED current
• Bandwidth of LED-PD1 link independent of LED current
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 (<280nm) LED in progress
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.