I am interested in PCA Photoconductive Antenna for THz waves.
Normally, a femtosecond laser is used to pump the PCA, but there exists other
technique to generate THz waves using two CW lasers. In this case the antenna
works as a photomixer.
Can I use your PCA as a photomixer?
See Appl. Opt. 47, 3023 (2008)
PCA  Photoconductive Antenna for terahertz waves  Questions and Answers
Del Mar Photonics  PCA brochure  buy online
Q:
What is maximum allowed incident pulse energy for PCA440610800x? If I use
this detector with ~1 kHz repetition rate laser, instead of
typical ~100 MHz repetition rate laser, does it make a big difference? For
example, shall I choose a detector with a larger gap?
A:
The maximum fluence on the antenna is 0.5mJ/cm^2. In dependence of the pulse
energy of the laser the spot size has to be choosen so, that the fluence does
not exceed this value. The resulting spot diameter on the antenna can be about
the same as the gap distance.
We have antennas with the following gap distance in stock:
6 micron, 10 micron, 14 micron, 16 micron, and 34 micron.
Q:
Could you explain the detector performance difference between PCA440610800,
PCA441616800, and PCA4434100800? different sensitivity, bandwidth or
something else?
A:
The best detector sensitivity for a given laser
excitation power on the antenna has the type PCA440610800. The reason for
that is the small gap distance of 6 microns.
The bandwidth is the same for the antennas
PCA440610800, PCA441616800, and PCA4434100800. It is weekly
dependent on the antenna length of 44 microns.
I recommend the use of the antenna
PCA440610800 as detector.
Q:
Thanks for your reply. I checked your website. I am interested in
PCA440610800x, PCA441616800x, and PCA4434100800x. Could you tell
me what is difference between PCAs of different gap width and distance? I am
looking for a THz detector using with 1 kHz repetition
rate femtosecond laser. Could you provide me a quotation for both unmounted and
mounted chip?
A:
For a photoconductive THz detector application the antenna with a small gap
PCA440610800x can be recommended. The detector current is proportional to
the product of the THz field and the semiconductor conductivity. In case of a
small gap distance a low electrical resistance between the electrodes is
possible to produce with a low laser power. The gap width has no significant
influence on the electrical behavior of the antenna.
Q:
I have two questions.
First, I know that an antenna with a gap distance of 6 um has the best
sensitivity among your products. But, I have to consider a bandwidth as well as
a sensitivity. Can you provide an antenna with a gap distance of 6 um and a
resonance frequency of 1.5 THz?
Second, in case of a resonance frequency of 1.5 THz, I would like to know the
bandwidth.
A:
The gap distance must be low especially for detector antennas to get high
sensitivity with a low laser power, focused into the small gap. A larger gap may
be also o.k., but this needs on the detector side a larger spot, because the
spot size has to be a little bit larger than the gap.
For the use as emitter antenna the spot size can be smaller than the antenna
gap. The metallic contacts must not be short circuited by the laser spot. It can
be also expected, that the emitted THz power increases with increasing pulse
power (and also voltage). Therefore for the emitter some people prefer antennas
with a larger gap.
The devices, which we have now in stock are the first attempt. We have learned,
that the actual antennas are very sensitive both as emitter or
detector for low frequencies up to 200 GHz. The reason for this high low
frequency sensitivity is the structure of the bond contact pads. This does not
decrease the sensitivity at 1 THz, but increases the sensitivity at lower
frequencies.
We prepare now new PCAs with the aim to increase the sensitivity in the 1  3
THz band and decrease it below 1 THz. The usefulness depends on the
application. The low frequency sensitivity must not be a disadvantage, because
for some interesting applications this frequency range is very convenient.
Q:
In your drawing of the antenna layout, you extend "L = lambda/2" into the bias
strip lines of the structure. It has been my understanding that the antenna
itself ends at the strip line (i.e. only the center of the H). Can you explain
this?
A:
I think, that the antenna length is determined by the length of the metal film,
in which the electrons can move in one direction. If the geometry is changed in
such a way, that the width of the two strip lines is drastically increased (e.g.
up to some hundreds of microns) the corresponding half wave resonance of this
long antenna shifts into the GHz range.
Your questions have been answered by Wolfgang Richter. Email your questions about Photoconductive Antennas or Saturable Absorber Mirror
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PCA  
Photoconductive Antenna for terahertz waves 

800 nm  
PCA with LTGaAs absorber for laser excitation wavelengths λ ≤ 850 nm; optical absorption > 70% 
Model  Product Name+  Price  Buy Now 
PCA441616800u  PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 16 µm  $825.00  
PCA441616800h  PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 16 µm  $1,950.00  
PCA4434100800u  PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 34 µm  $825.00  
PCA4434100800h  PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 34 µm  $1,950.00  
PCA440610800u  PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 6 µm  $825.00  
PCA440610800h  PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 6 µm  $1,950.00  
PCA301010800u  PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 10 µm  $825.00  
PCA301010800h  PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 10 µm  $1,950.00  
PCA301414800u  PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 14 µm  $825.00  
PCA301414800h  PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 14 µm  $1,950.00 
Displaying 1 to 10 (of 10 products) 
9901060 nm  
PCA with LTGaAs absorber for laser excitation wavelengths λ = 990 .. 1060 nm; optical absorption ~ 50% 
Displaying 1 to 10 (of 10 products) 
1040 nm  
PCA with LTGaAs absorber for laser excitation wavelengths λ ~ 1040 nm; optical resonant design 97% absorption @ 1040 nm 
Model  Product Name+  Price  Buy Now 
PCA4416161040h  PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 16 µm  $1,950.00  
PCA4416161040u  PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 16 µm  $825.00  
PCA44341001040h  PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 34 µm  $1,950.00  
PCA44341001040u  PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 34 µm  $825.00  
PCA4406101040h  PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 6 µm  $1,950.00  
PCA4406101040u  PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 6 µm  $825.00  
PCA3010101040u  PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 10 µm  $825.00  
PCA3010101040h  PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 10 µm  $1,950.00  
PCA3014141040h  PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 14 µm  $1,950.00  
PCA3014141040u  PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 14 µm  $825.00 
Displaying 1 to 10 (of 10 products) 
iPCA  
interdigital Photoconductive Antenna for terahertz waves 
Model  Product Name+  Price  Buy Now 
iPCAp21051000800  iPCAp, 800 nm, 21x5x1000 microns  $2,880.00  
iPCAp2105300800  iPCAp, 800 nm, 21x5x300 microns  $2,720.00  
iPCAs21051000800  iPCAs, 800 nm, 21x5x1000 microns  $2,880.00  
iPCAs2105300800  iPCAs, 800 nm, 21x5x300 microns  $2,720.00 
Displaying 1 to 4 (of 4 products) 