外文翻譯---用于量子密鑰的單光子apd探測(cè)器設(shè)計(jì)

1、<p>　　Design and Characterization of Single Photon APD Detector for QKD Application</p><p><b>　　Abstract</b></p><p>　　Modeling and design of a single photon detector and its var

2、ious characteristics are presented. It is a type of avalanche photo diode (APD) designed to suit the requirements of a Quantum Key Distribution (QKD) detection system. The device is modeled to operate in a gated mode at

3、liquid nitrogen temperature for minimum noise and maximum gain. Different types of APDs are compared for best performance. The APD is part of an optical communication link, which is a private channel to transmit the key

4、s</p><p>　　I. INTRODUCTION</p><p>　　Photon detectors sensitive to extremely low light levels are needed in a variety of applications. It was not possible to introduce these devices commercially

5、several years ago because of the stringent requirements of QKD. Research efforts however resulted in photon detectors with reasonably good performance characteristics. The objective here is to model a single photon detec

6、tor of high sensitivity, suitable for a QKD system. The detector is basically an APD, which needs cooling to very low temp</p><p>　　Attacks on communication systems in recent years have become a main concern

7、 accompanying the technological advances. The measures and counter measures against attacks have driven research effort towards security techniques that aim at absolute infallibility. Quantum Mechanics is considered one

8、of the answers, due to inherent physical phenomena. QKD systems which depend on entangled pairs or polarization states will inevitably require the usage of APDs in photon detection systems. How suitable th</p><

9、;p>　?、? AVALANCHE PHOTO DIODE</p><p>　　A. Structure of the APD </p><p>　　Fig. 1 shows a schematic diagram of the structure of an APD. The APD is a photodiode with a built-in amplification m

10、echanism. The applied reverse potential difference causes accelerates photo-generated carriers to very high speeds so that a transfer of momentum occurs upon collisions, which liberates other electrons. Secondary electro

11、ns are accelerated in turn and the result is an avalanche process. The photo generated carriers traverse the high electric field region causing further ionization b</p><p>　　The number of ionization collisio

12、ns per unit length for holes and electrons is designated ionization coefficients αn and αp, respectively. The type of materials and their band structures are responsible for the variation in αn and αp. Ionization coeffic

13、ients also depend on the applied electric field according to the following relationship: </p><p><b>　　(1) </b></p><p>　　For αn = αp = α, the multiplication factor, M takes the form

14、 </p><p><b>　　(2) </b></p><p>　　W is the width of the depletion region. It can be observed that M tends to ∞ when αW →1, which signifies the condition for junction breakdown. There

15、fore, the high values of M can be obtained when the APD is biased close to the breakdown region. </p><p>　　The thickness of the multiplication region for M = 1000, has been calculated and compared with those

16、 found by other workers and the results are shown in Table 1. The layer thickness for undoped InP is 10μm, for a substrate thickness of 100μm. </p><p>　　The photon-generated electron-hole pairs in the abso

17、rption layer are accelerated under the influence of an electric field of 3.105V/cm. The acceleration process is constantly interrupted by random collisions with the lattice. The two competing processes will continue unti

18、l eventually an average saturation velocity is reached. Secondary electron-hole pairs are generated at any time during the process, when they acquire energy larger than the band gap Eg. The electrons are then accelerate

19、d and ma</p><p>　　Impact ionization of holes due to bound electrons is not as effective as that due to free electrons. Hence, most of the ionization is achieved by free electrons. The avalanche process then

20、proceeds principally from the p to the n side of the device. It terminates after a certain time, when the electrons arrive at the n side of the depletion layer. Holes moving to the left create electrons that move to the

21、right, which in turn generate further holes moving to the left in a possibly unending circu</p><p>　　It may be desirable to fabricate APDs from materials that permit impact ionization by only one type of car

22、riers either electrons or holes. Photo detector materials generally exhibit different ionization rates for electrons and holes. The ratio ofthe two ionization rates k = βi/αi is a measure of the photodiode performance. I

23、f for example, electrons have higher ionization coefficient, optimal behavior is achieved by injecting electrons of photo-carrier pairs at the p-type edge of the depletion la</p><p>　　Geiger Mode</p>

24、<p>　　Geiger mode (GM) operation means that the diode is operated slightly above the breakdown threshold voltage, where a single electron–hole pair can trigger a strong avalanche. In the case of such an event, the e

25、lectronics reduce the diode voltage to below the threshold value for a short time called “dead time”, during which the avalanche is stopped and the detector is made ready to detect the next batch of photons. GM operation

26、 is one of the basic of Quantum Counting techniques when utilizing an a</p><p>　　There are a number of parameters related to Geiger mode. The general idea however is to temporarily disturb the equilibrium in

27、side the APD.</p><p>　　The Geiger mode is placing the APD in a gated regime and the bias is raised above the breakdown voltage for a short period of time. Fig. 2 shows the parameters characterizing the Geige

28、r operation. The rise and fall times of the edges are neglected because they are made fast. Detection of single photons occurs during the gate window.</p><p>　　作者：Khalid A. S. Al-Khateeb, Nazmus Shaker Nafi,

29、 Khalid Hasan</p><p><b>　　國(guó)籍：美國(guó)</b></p><p>　　出處：Computer and Communication Engineering (ICCCE), 2010 International Conference on 11-12 May 2010</p><p>　　用于量子密鑰的單光子A

30、PD探測(cè)器設(shè)計(jì) </p><p><b>　　摘要</b></p><p>　　本文提出的是單光子探測(cè)器及其各種特性的建模與設(shè)計(jì)。它是利用雪崩光電二極管（APD）的一種特性，以適應(yīng)量子密鑰分配（QKD）檢測(cè)系統(tǒng)的要求。該設(shè)備是在液氮溫度下按門(mén)控模式運(yùn)行，以便使其噪聲最小和增益最大。通過(guò)不同類型的APD相比，以獲得性能最佳的探測(cè)器。APD是用來(lái)傳輸關(guān)鍵信號(hào)的私人光通信號(hào)

31、通路的一部分。通過(guò)一個(gè)公共的通道發(fā)送加密的消息。光電通路的工作波為1.55μm。這是在InGaAs的量子效率超過(guò)75％，和倍增因子為1000基礎(chǔ)上設(shè)計(jì)的。計(jì)算所得的暗電流低于10-12A，且整體信噪聲比高于18分貝??。該器件的靈敏度高于-40dBm的，比暗電流多一個(gè)量級(jí)，相當(dāng)于在微微秒脈沖時(shí)檢測(cè)到兩個(gè)光子的靈敏度。這里的目標(biāo)是，以單光子探測(cè)器靈敏度高，適合的量子密碼系統(tǒng)的建模。</p><p><b>

32、;　　引言</b></p><p>　　在各種應(yīng)用中，有些需要對(duì)微弱光敏感的光子探測(cè)器。在幾年前是不可能引進(jìn)這些設(shè)備的，因?yàn)榱孔用荑€技術(shù)的要求嚴(yán)格。然而隨著研究發(fā)展，發(fā)明了有合理性能等特點(diǎn)的光子探測(cè)器的。這里的目標(biāo)是建一個(gè)靈敏度高的單光子探測(cè)器，來(lái)適應(yīng)量子密碼系統(tǒng)。APD探測(cè)器需要把它冷卻到非常低的溫度（77K），以便其暗電流很小。探測(cè)器的探測(cè)波長(zhǎng)為1.55μm。不同的應(yīng)用設(shè)計(jì)可能會(huì)提出不同的要求，因

33、此需參照波長(zhǎng)，溫度，響應(yīng)度，暗電流，噪聲等各種參數(shù)。比較來(lái)自計(jì)算的結(jié)果，在此基礎(chǔ)上找到并提供適合特殊應(yīng)用的合適的APD探測(cè)器。</p><p>　　近年來(lái)伴隨著科技進(jìn)步，通信系統(tǒng)的研究已成為一個(gè)主要的關(guān)注方向。隨著避免受攻擊措施和對(duì)策的提出，推動(dòng)著研究工作朝安全技術(shù)發(fā)展，旨在不發(fā)生錯(cuò)誤。由于其固有的物理現(xiàn)象，量子力學(xué)被認(rèn)為是一種方法。依賴于空穴-電子對(duì)或偏振態(tài)的量子密碼系統(tǒng)，將不可避免地需要使用的APD的光子探測(cè)

34、系統(tǒng)。如何找到合適的些探測(cè)器，取決于它們對(duì)微光信號(hào)檢測(cè)的能力，換句話說(shuō)就是“光子計(jì)數(shù)” 。因此，預(yù)計(jì)高安全性系統(tǒng)的將應(yīng)用在多種領(lǐng)域，如銀行業(yè)，軍事，醫(yī)療，電子商務(wù)，電子政務(wù)等。</p><p>　　2. 雪崩光電二極管</p><p><b>　　A. APD的結(jié)構(gòu)</b></p><p>　　APD結(jié)構(gòu)如圖1所示。APD是一個(gè)帶有一個(gè)內(nèi)置的放

35、大機(jī)制的光電二極管。在其上施加反向的電位差使光生載流子加速度，使其轉(zhuǎn)移的時(shí)與原子發(fā)生碰撞，從而解放其他電子。新產(chǎn)生的電子再次加速，重復(fù)上述過(guò)程，導(dǎo)致發(fā)生雪崩。生成的光生載子轉(zhuǎn)移到高電場(chǎng)區(qū)域與價(jià)帶中束縛中釋放出來(lái)的電子碰撞后，發(fā)生進(jìn)一步的電離。這個(gè)電子-空穴對(duì)的生成過(guò)程被稱為碰撞電離過(guò)程。當(dāng)載流子與原子發(fā)生碰撞時(shí)，他們就給原子一些能量。如果載流子的動(dòng)能大于帶隙，碰撞時(shí)就會(huì)釋放出一個(gè)束縛著的電子。獲得足夠的能量的電子-空穴對(duì)，還能引起進(jìn)一步

36、的碰撞電離。其結(jié)果就是發(fā)生雪崩，自由載流子的數(shù)量呈指數(shù)增長(zhǎng)的進(jìn)程??繼續(xù)下去。</p><p>　　圖1 APD結(jié)構(gòu)如圖</p><p>　　電離碰撞電離系數(shù)αn和αP分別代表每單位長(zhǎng)度內(nèi)電離碰撞產(chǎn)生的電子和空穴的數(shù)目。材料及其能帶結(jié)構(gòu)影響αn和αP的參數(shù)變化。依賴于外加電場(chǎng)的電離系數(shù)有以下關(guān)系式：</p><p><b>　　(1)</b>&

37、lt;/p><p>　　其中αn=αp=α，而倍增因子M有以下形式：</p><p><b>　　(2)</b></p><p>　　W是耗盡區(qū)的寬度?？梢杂^察到當(dāng)αW→1時(shí)，的M趨于無(wú)窮，這是發(fā)生擊穿的條件。因此，當(dāng)APD偏置接近擊穿區(qū)條件時(shí)，就可以得到高的M值。</p><p>　　M = 1000的倍增區(qū)厚度的計(jì)算，并

38、與其他已知的材料比較，結(jié)果表1所示。在厚度為100μm的襯底中摻雜InP層的厚度為10微米。</p><p>　　表1 APD的各層厚度和特性</p><p>　　在一個(gè)3.105V/cm電場(chǎng)的作用下，吸收層中光子產(chǎn)生的電子 - 空穴對(duì)被加速。加速過(guò)程中，它不斷地隨機(jī)與原子發(fā)生碰撞。這兩個(gè)相互競(jìng)爭(zhēng)的過(guò)程將不斷持續(xù)下去，直到最終平均飽和速度的達(dá)到。隨著進(jìn)程的持續(xù)，當(dāng)他們獲得的能量大于電勢(shì)能，

39、二次電子 - 空穴對(duì)的在任何時(shí)候都可產(chǎn)生。電子的加速可能導(dǎo)致進(jìn)一步的碰撞電離。 </p><p>　　空穴與束縛電子的碰撞電離效率低于自由電子的碰撞電離。因此，最重要的是實(shí)現(xiàn)自由電子電離。雪崩過(guò)程就是碰撞電離過(guò)程從設(shè)備的P區(qū)發(fā)生到N區(qū)的過(guò)程。它在電子到達(dá)N區(qū)耗盡層后的一定時(shí)間內(nèi)終止?？?/p>

40、穴移動(dòng)到左邊使電子移動(dòng)右邊，這反過(guò)來(lái)使空穴移到左邊，這一過(guò)程循環(huán)往復(fù)發(fā)生。這個(gè)反饋過(guò)程中，雖然增加了設(shè)備的增益，但它仍然是有以下幾個(gè)不良因素。首先，它費(fèi)時(shí)且降低了設(shè)備的帶寬。其次，它是一個(gè)隨機(jī)過(guò)程，并因此增加了設(shè)備的噪音。第三，它是不穩(wěn)定的，可能導(dǎo)致雪崩擊穿。</p><p>　　允許只有一個(gè)載流子（無(wú)論是電子或空穴）發(fā)生碰撞電離過(guò)程的材料，用來(lái)制作APD是可取的。對(duì)于電子和空穴，光電探測(cè)器材料普遍有不同的電離率

41、果。兩個(gè)電離率比例K =βi/αi是一個(gè)光電二極管的性能的測(cè)量方法。例如，如果電子具有較高的電離系數(shù)，最好的方法是通過(guò)在耗盡層p型邊緣的注入攜帶光子對(duì)的電子，并使用K值盡可能小的材料。如果是空穴注入，應(yīng)注入到耗盡層n型邊緣和并k值要應(yīng)該盡可能大。單載波倍增理想實(shí)現(xiàn)的條件是 k = 0（電子）或與K =∞（空穴）。</p><p><b>　　Geiger模型</b></p>&

42、lt;p>　　蓋格爾模式（GM）就是加在二極管的運(yùn)行電壓略高于擊穿閾值電壓，可以使單一的電子 - 空穴對(duì)引發(fā)強(qiáng)烈雪崩。在這種模式下，電子減少二極管電壓將在很短的時(shí)間快速減到低于閾值，這被稱為“死區(qū)時(shí)間”，在此期間探測(cè)器雪崩停止和并準(zhǔn)備檢測(cè)下一批光子。當(dāng)利用雪崩過(guò)程（APD）提高了探測(cè)器的效率后，蓋格爾模式就成為了量子計(jì)算技術(shù)的基礎(chǔ)之一。</p><p>　　這里有蓋格爾模式相關(guān)的參數(shù)。但總的想法是暫時(shí)擾亂A

43、PD的內(nèi)部平衡。</p><p>　　圖2 蓋格爾操作模式圖</p><p>　　蓋格爾模式吧APD放置在門(mén)控模式下工作，并使偏置電源能在很短的時(shí)間內(nèi)，提供高于擊穿電壓的電壓。圖2顯示的參數(shù)表征了蓋格爾操作模式。上升沿和下降沿時(shí)間可被忽視，因?yàn)樗鼈儼l(fā)生的很快。</p><p>　　作者：Khalid A. S. Al-Khateeb, Nazmus Shaker N