Del Mar Photonics

 

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 PCA-44-06-10-800-x? 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 PCA-44-06-10-800, PCA-44-16-16-800, and PCA-44-34-100-800? different sensitivity, bandwidth or something else?

A:
The best detector sensitivity for a given laser excitation power on the antenna has the type PCA-44-06-10-800. The reason for that is the small gap distance of 6 microns. The bandwidth is the same for the antennas PCA-44-06-10-800, PCA-44-16-16-800, and PCA-44-34-100-800. It is weekly dependent on the antenna length of 44 microns. I recommend the use of the antenna PCA-44-06-10-800 as detector.

Q:
Thanks for your reply. I checked your website. I am interested in PCA-44-06-10-800-x, PCA-44-16-16-800-x, and PCA-44-34-100-800-x. 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 PCA-44-06-10-800-x 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. E-mail your questions about Photoconductive Antennas or Saturable Absorber Mirror

Wolfgang Richter

Del Mar Photonics - PCA brochure - buy online

 

PCA
PCA Photoconductive Antenna for terahertz waves


800 nm

990-1060 nm

1040 nm
800 nm
 
PCA with LT-GaAs absorber for laser excitation wavelengths λ ≤ 850 nm; optical absorption > 70%

 Model   Product Name+   Price   Buy Now 
 PCA-44-16-16-800-u   PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 16 Ám   $825.00  Buy Now 
 PCA-44-16-16-800-h   PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 16 Ám   $1,950.00  Buy Now 
 PCA-44-34-100-800-u   PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 34 Ám   $825.00  Buy Now 
 PCA-44-34-100-800-h   PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 34 Ám   $1,950.00  Buy Now 
 PCA-44-06-10-800-u   PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 6 Ám   $825.00  Buy Now 
 PCA-44-06-10-800-h   PCA: resonance frequency 1 THz, λ = 800 nm, gap distance 6 Ám   $1,950.00  Buy Now 
 PCA-30-10-10-800-u   PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 10 Ám   $825.00  Buy Now 
 PCA-30-10-10-800-h   PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 10 Ám   $1,950.00  Buy Now 
 PCA-30-14-14-800-u   PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 14 Ám   $825.00  Buy Now 
 PCA-30-14-14-800-h   PCA: resonance frequency 1.5 THz, λ = 800 nm, gap distance 14 Ám   $1,950.00  Buy Now 
Displaying 1 to 10 (of 10 products)
990-1060 nm
 
PCA with LT-GaAs absorber for laser excitation wavelengths λ = 990 .. 1060 nm; optical absorption ~ 50%

 Model   Product Name+   Price   Buy Now 
 PCA-44-16-16-1030-h   PCA: resonance frequency 1 THz, λ = 990 .. 1060 nm, gap distance 16 Ám   $1,950.00  Buy Now 
 PCA-44-16-16-1030-u   PCA: resonance frequency 1 THz, λ = 990 .. 1060 nm, gap distance 16 Ám   $825.00  Buy Now 
 PCA-44-34-100-1030-u   PCA: resonance frequency 1 THz, λ = 990 .. 1060 nm, gap distance 34 Ám   $825.00  Buy Now 
 PCA-44-34-100-1030-h   PCA: resonance frequency 1 THz, λ = 990 .. 1060 nm, gap distance 34 Ám   $1,950.00  Buy Now 
 PCA-44-06-10-1030-u   PCA: resonance frequency 1 THz, λ = 990 .. 1060 nm, gap distance 6 Ám   $825.00  Buy Now 
 PCA-44-06-10-1030-h   PCA: resonance frequency 1 THz, λ = 990 .. 1060 nm, gap distance 6 Ám   $1,950.00  Buy Now 
 PCA-30-10-10-1030-h   PCA: resonance frequency 1.5 THz, λ = 990 .. 1060 nm, gap distance 10 Ám   $1,950.00  Buy Now 
 PCA-30-10-10-1030-u   PCA: resonance frequency 1.5 THz, λ = 990 .. 1060 nm, gap distance 10 Ám   $825.00  Buy Now 
 PCA-30-14-14-1030-u   PCA: resonance frequency 1.5 THz, λ = 990 .. 1060 nm, gap distance 14 Ám   $825.00  Buy Now 
 PCA-30-14-14-1030-h   PCA: resonance frequency 1.5 THz, λ = 990 .. 1060 nm, gap distance 14 Ám   $1,950.00  Buy Now 
Displaying 1 to 10 (of 10 products)
1040 nm
 
PCA with LT-GaAs absorber for laser excitation wavelengths λ ~ 1040 nm; optical resonant design 97% absorption @ 1040 nm

 Model   Product Name+   Price   Buy Now 
 PCA-44-16-16-1040-h   PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 16 Ám   $1,950.00  Buy Now 
 PCA-44-16-16-1040-u   PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 16 Ám   $825.00  Buy Now 
 PCA-44-34-100-1040-h   PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 34 Ám   $1,950.00  Buy Now 
 PCA-44-34-100-1040-u   PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 34 Ám   $825.00  Buy Now 
 PCA-44-06-10-1040-h   PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 6 Ám   $1,950.00  Buy Now 
 PCA-44-06-10-1040-u   PCA: resonance frequency 1 THz, λ ~ 1040 nm, gap distance 6 Ám   $825.00  Buy Now 
 PCA-30-10-10-1040-u   PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 10 Ám   $825.00  Buy Now 
 PCA-30-10-10-1040-h   PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 10 Ám   $1,950.00  Buy Now 
 PCA-30-14-14-1040-h   PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 14 Ám   $1,950.00  Buy Now 
 PCA-30-14-14-1040-u   PCA: resonance frequency 1.5 THz, λ ~ 1040 nm, gap distance 14 Ám   $825.00  Buy Now 
Displaying 1 to 10 (of 10 products)  

 

iPCA
 
interdigital Photoconductive Antenna for terahertz waves

 Model   Product Name+   Price   Buy Now 
 iPCAp-21-05-1000-800   iPCAp, 800 nm, 21x5x1000 microns   $2,880.00  Buy Now 
 iPCAp-21-05-300-800-   iPCAp, 800 nm, 21x5x300 microns   $2,720.00  Buy Now 
 iPCAs-21-05-1000-800   iPCAs, 800 nm, 21x5x1000 microns   $2,880.00  Buy Now 
 iPCAs-21-05-300-800-   iPCAs, 800 nm, 21x5x300 microns   $2,720.00  Buy Now 
Displaying 1 to 4 (of 4 products)