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InGaAs増幅フォトディテクター、ファイバー結合型![]()
PDA8GS Fixed Gain FPD610-FC-NIR Fixed Gain
FPD310-FC-NIR Switchable Gain ![]() Please Wait
![]() Click to Enlarge 9.5 GHz増幅フォトディテクタPDA8GSの使用例 特長
当社では近赤外の波長域に感度のあるファイバ結合型のInGaAs増幅フォトディテクタをご用意しております。これらの高速応答ディテクタは、高速レーザーパルス、低光量信号、あるいは断続光などの検出に適しています。すべてのディテクタに電源が付属します。 PDA8GS FPD310-FC-NIR FPD510-FC-NIR&FPD610-FC-NIR 自由空間光向けのInGaAsフォトディテクタについてはこちらをご覧ください。
PDA8GS信号出力:SMAメス型 |
計算式 | ||||
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平均パワーから算出するピークパワー、ピークパワーから算出する平均パワー : | ||||
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平均パワーおよびデューティーサイクルから算出するピークパワー*: | ||||
![]() | *デューティーサイクル(![]() |
図1: パルスレーザ光の特性を記述するためのパラメータを、上のグラフと下の表に示します。パルスエネルギ (E)は、パルス曲線の下側の黄色の領域の面積に対応します。このパルスエネルギは斜線で表された領域の面積とも一致します。
パラメータ | シンボル | 単位 | 説明 | ||
---|---|---|---|---|---|
パルスエネルギ | E | ジュール[J] | レーザの1周期中に放射される1パルスの全放射エネルギ。 パルスエネルギはグラフの黄色の領域の面積に等しく、 これは斜線部分の面積とも一致します。 | ||
周期 | Δt | 秒 [s] | 1つのパルスの開始から次のパルスの開始までの時間 | ||
平均パワー | Pavg | ワット[W] | パルスとして放射されたエネルギが、1周期にわたって 均一に広がっていたと仮定したときの、 光パワーの大きさ(光パワー軸上の高さ) | ||
瞬時パワー | P | ワット[W] | 特定の時点における光パワー | ||
ピークパワー | Ppeak | ワット [W] | レーザから出力される最大の瞬時パワー | ||
パルス幅 | ![]() | 秒 [s] | パルスの開始から終了までの時間。一般的にはパルス形状の 半値全幅(FWHM)を基準にしています。 パルス持続時間とも呼ばれます。 | ||
繰り返し周波数 | frep | ヘルツ [Hz] | パルス光が放射される頻度を周波数で表示した量。 周期とは逆数の関係です。 |
計算例
下記のパルスレーザ光を測定するのに、最大入力ピークパワーが75 mW
のディテクタを使用するのは安全かどうかを計算してみます。
1パルスあたりのエネルギは、
と低いようですが、ピークパワーは、
となります。このピークパワーはディテクタの
最大入力ピークパワーよりも5桁ほど大きく、
従って、上記のパルスレーザ光を測定するのに
このディテクタを使用するのは安全ではありません。
Posted Comments: | |
user
 (posted 2019-05-09 13:43:00.173) I have similar question that was posed to ThorLabs in past. Generally the detectors with GHz response have lower frequency cut-off of few 10s of kHz. Also AC coupled versions do not detect CW component. PDA8GS seems to be an exception. Can PDA8GS display DC and few kHz pulse trains (with pulses of slow rise /fall times few ns) without distortion? If a signal has DC and AC components, Can PDA8GS be used detect pulsed signal and its DC background (CW component)?
Below is similar question from past from someone else for your ready reference.
-Srikanth
kedves (posted 2017-05-11 15:07:06.75)
Dear Thorlabs, let me inquire about the frequency characteristics of PDA8GS. Is the transfer function over the whole frequency range DC-9.5 GHz smooth? I am asking this because we have fast amplified photoreceivers of another manufacturer which have a crossover region (at about 25-100 KHz) between the DC and AC responses leading to a distorted output signal to e.g. a step function input. What is the response of this detector to a step function? Is there any visible transition between the DC and high frequency ranges? Thanks
nbayconich (posted 2017-06-07 05:03:14.0)
Thank you for contacting Thorlabs. We are currently looking into measuring the bandwidth frequency characteristics of the PDA8GS. A techsupport representative will contact you directly with more information. asundararaj
 (posted 2019-05-09 07:27:47.0) Thank you for contacting Thorlabs. The PDA8GS is a DC coupled detector and hence, it can detect both CW and and ~kHz pulsed components of the signal. I have contacted you directly via email to discuss this further. minowa
 (posted 2018-09-24 06:14:47.367) Hi, could you provide the information about the NEP of PDA8GS? YLohia
 (posted 2018-09-24 01:17:12.0) Hello, thank you for contacting Thorlabs. The dark current, at 25°C, is typically <10nA, and at 55°C is typically <50nA. The NEP for the fiber-optic receiver is:
NEP (rms)
1.5uW typical @ 1310nm
3.0uW maximum @ 1310nm
2.5uW typical @ 850nm
5.0uW maximum @ 850nm
Recently, we performed a preliminary test with 1550nm, and found that the input referred noise = 1.5uW rms (with 9.5GHz bandwidth).
Assuming a white noise distribution over the 9.5GHz bandwidth, this implies NEP = 15pW/rt-Hz. These numbers then scale inversely with responsivity at other wavelengths.
Please note that this only sample data and is not necessarily representative of our current units. These values presented are not a guaranteed performance. kedves
 (posted 2017-05-11 15:07:06.75) Dear Thorlabs, let me inquire about the frequency characteristics of PDA8GS. Is the transfer function over the whole frequency range DC-9.5 GHz smooth? I am asking this because we have fast amplified photoreceivers of another manufacturer which have a crossover region (at about 25-100 KHz) between the DC and AC responses leading to a distorted output signal to e.g. a step function input. What is the response of this detector to a step function? Is there any visible transition between the DC and high frequency ranges? Thanks nbayconich
 (posted 2017-06-07 05:03:14.0) Thank you for contacting Thorlabs. We are currently looking into measuring the bandwidth frequency characteristics of the PDA8GS. A techsupport representative will contact you directly with more information. makarov
 (posted 2016-05-26 14:11:44.267) PDA8GS actually dies if the optical power rating is exceeded. This was a surprise to us. The maximum rating is 1 mW CW. We did not pay attention initially, because we thought the front-end photodied surely takes much more that 1 mW to get physically damaged, and what else could go wrong? It has turned out, the RF amplifier dies. Our units just came back from a lengthy and costly repair. I with it were stated in the spec sheet that damage to the RF amplifier will result from exceeding the optical power.
We have similar amplified photodetectors from LeCroy (OE455/555) and they do not die from optical overload, even though they get saturated at less than 1 mW just as this Thorlabs photodetector. besembeson
 (posted 2016-06-01 05:33:43.0) Response from Bweh at Thorlabs USA: This is actually a failure of the sensor material itself. To operate at these high speeds, the active area needs to be very small since the photodiode capacitance is directly correlated to active area. This is the limiting factor for electrical bandwidth. In this case, the fiber inserts against a ball lens that focuses all the light onto this very small active area sensor. The material damage threshold can easily be exceeded. Usually it looks like a very large dark current to the electronics where the gain is usually enough to saturate the output to the voltage rail. Since this is an integrated PD and amplifier package, the complete module needs to be replaced as a result of this - reason for the repair being more expensive than imagined. |
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