| 摘要: | 量子科技在近年來逐漸成為熱門話題，諸如擁有高度安全性的量子通訊和能夠快速解決複雜問題的量子計算更是受到高度關注。在這些領域中，擁有光子數解析（Photon number resolving, PNR）能力的光偵測器扮演著至關重要的角色，相較於單顆元件僅依靠自身能力所進行的光子數解析，陣列元件採用多個元件訊號並聯輸出的方式能夠具有更佳的光子數解析能力，以往的陣列元件常以矽為基底的光偵測器亦或是超導奈米材料所組成，本文則是選擇以III-V族材料所製成的單光子雪崩二極體(Single Photon Avalanche Diode, SPAD)元件來組成陣列，相對於其他光偵測器，III-V族材料製成的SPAD在操作上不需要像超導奈米材料一樣在極低溫下運作，而且由於三五族材料應用在不可見光的波段，也較SiPM不易受到可見光的干擾。此外，在光通訊領域中，也能夠作為接收光子的偵測器，適用於1550 nm波段的量子密鑰分發(quantum key distribution, QKD)上，並可應用在光纖通訊上。
本文使用實驗室自製的InGaAs/InAlAs SPAD元件進行量測，採用閘控模式操作，條件設定為104.731MHz的閘控頻率以及26.18275MHz的雷射頻率，脈衝寬度則為1.5ns，並搭配自差分電路以消除電容耦合訊號。在平均光子數設定為1顆的條件下分別針對單顆元件以及2x2陣列元件的光子數解析能力進行分析比較，單顆元件在46%的單光子偵測效率下解析出了5顆光子，而陣列元件則在14.8%的單光子偵測效率下實現了6顆光子的解析，此外，也比較了兩元件的光子數解析參數，在電壓峰值分離度、半高寬以及品質因數(FOM)上，陣列元件也都優於單顆元件，這說明了SPAD元件的陣列形式能提供更好的光子數解析能力。
;Quantum technology has been gaining popularity in recent years, with a strong focus on areas such as quantum communication, known for its high security, and quantum computing, capable of solving complex problems rapidly. In these domains, photon number resolving (PNR) capabilities of photodetectors play a crucial role. Compared to single-element photodetectors that rely solely on their intrinsic capabilities for photon number resolution, array elements that use multiple component signals in parallel output can offer superior photon number resolving capabilities. Traditionally, array elements have been composed of silicon-based photodetectors or superconducting nano materials. However, this article opts for the use of III-V semiconductor materials to fabricate single photon avalanche diode (SPAD) elements for array construction. Relative to other photodetectors, III-V semiconductor-based SPADs do not require operation at extremely low temperatures like superconducting nano materials. Additionally, since III-V materials are used in the infrared spectrum, they are less susceptible to interference from visible light compared to Silicon Photomultipliers (SiPMs). Furthermore, in the field of optical communication, these SPADs can also serve as photon detectors, making them suitable for Quantum Key Distribution (QKD) in the 1550 nm wavelength range and applicable to optical fiber communication as well.
This paper presents measurements conducted using self-developed and self-fabricated InGaAs/InAlAs SPAD devices operated in gating mode. The experimental conditions were set with a gating frequency of 104.731 MHz and a laser frequency of 26.18275 MHz which has a pulse width of 1.5 ns. Additionally, self-differential circuits were employed to eliminate capacitive-coupled signals. Under the condition of an average photon number set to 1, the photon number resolving capabilities of both single-device and 2x2 array device were analyzed and compared. The single-device achieved the resolution of 5 photons at a single photon detection efficiency of 46%, whereas the array device achieved the resolution of 6 photons at a single photon detection efficiency of 14.8%. Furthermore, a comparison of the photon number resolving parameters between the two types of devices, including peak voltage separation, full-width at half-maximum, and figure of merit (FOM), demonstrated that the array device outperformed the single-device, which indicates that the array device provides superior photon number resolving capabilities over the single-device. |
