科學(xué)家發(fā)明出一種針孔大小的微型激光器能精確的辨識(shí)和計(jì)量單個(gè)的病毒，它還可以用于計(jì)量云的形成過(guò)程中或者我們呼吸的空氣中的污染物納米粒子。

　　當(dāng)顆粒物落到環(huán)上面的時(shí)候，從微型激光器發(fā)出的光受到干擾，研究員就通過(guò)這種方式改變光的頻率。在噪音環(huán)境中失去信號(hào)之前，該環(huán)狀激光器可以順序計(jì)量800個(gè)納米粒子。通過(guò)刺激多個(gè)模式，科學(xué)家可以更加確定計(jì)量的準(zhǔn)確性。通過(guò)改變?cè)鲆娼橘|(zhì)，可以使用水下傳感器替代空氣傳感器。

　　這種新型傳感器由華盛頓大學(xué)電氣和系統(tǒng)工程專業(yè)助理教授Lan Yang所帶領(lǐng)的團(tuán)隊(duì)研發(fā)出來(lái)。這項(xiàng)研究成果可廣泛用于商業(yè)的氣溶膠技術(shù)領(lǐng)域和生物學(xué)，關(guān)于此傳感器的更多細(xì)節(jié)發(fā)表在自然。納
 

米技術(shù)雜志上。

圖中右上方顯示顆粒物落到微型激光器上

　　不同于之前的回音壁諧振器，新型傳感器是一個(gè)小型激光器而不是外置激光器諧振腔。當(dāng)粒子與微型激光器相碰撞，這種微小的變化會(huì)產(chǎn)生兩種不同的頻率，這種頻率分裂可以通過(guò)在光電探測(cè)器中結(jié)合成不同的激光模式來(lái)測(cè)量。光電探測(cè)器能產(chǎn)生一種與此頻率差匹配的頻率。

　　Lan Yang指出：“微型激光器比被動(dòng)諧振器靈敏度更高，最大分辨率可達(dá)到1nm”

　　目前激光直接顯示為環(huán)形狀，與之前耦合到環(huán)型介質(zhì)中，整個(gè)系統(tǒng)可以自身調(diào)控，也更簡(jiǎn)單。“可以使用光源激活光學(xué)介質(zhì)，”Yang 說(shuō)道：“這樣就可以用一個(gè)廉價(jià)的激光二極管替代昂貴的可調(diào)諧激光器作為激活介質(zhì)了。”研究小組用不同材料和不同形狀的納米顆粒如：聚苯乙烯、金及病毒顆粒等測(cè)試了該微型激光器的性能。

　　該研究小組的下一步計(jì)劃是設(shè)計(jì)微型激光器的表面以識(shí)別DNA和單個(gè)的生物分子。由于DNA屬于工程納米粒子，微
 

型激光傳感器能計(jì)量每個(gè)DNA分子甚至分子碎片也能精確計(jì)量。

　原文如下：

A microlaser in the size of a pinprick has been developed that can identify and count inpidual viruses accurately. It can also be used to count the nanoparticles that initiate cloud formation or pollute the air we breathe.

The inset at the top right shows a particle landing on the microlaserLight from the micro-laser is disturbed when a particle sits on the ring, thus altering the frequency of light. The ring can count nanoparticles of the order of 800 before losing signals in the noise. By stimulating more than one mode, scientists can be doubly sure about the count’s accuracy. And by varying the gain medium, they can use the sensor for water instead of air.

The assistant professor of electrical and systems engineering at Washington University, Lan Yang led a team to create the new sensor, which can be used commercially in fields ranging from aerosol science to biology. Details on the sensor are recorded in Nature Nanotechnology.

The new sensor is different from previous whispering gallery resonators as it is a miniature laser instead of an external laser’s resonating cavity. When a particle comes in contact with the microlaser, two different frequencies with slight variations are generated. The frequency splitting can be measured by combining the split laser modes in a photodetector, which generates a beat frequency that matches the difference in frequency.

The microlaser offers high sensitivity than the passive resonator, Yang says. The maximum resolution achieved by the microlaser is about one nanometer.

When the laser is present in the ring, the whole system is self contained and simple rather than when it is coupled to the ring. The optical medium can be activated using a light source says Yang, and an inexpensive laser diode can be used in the place of an expensive tunable laser. The team tested the performance of the micro-laser using nanoparticles of different sizes and various materials, such as polystyrene, gold, and virions.

Next, the team wants to design the tiny microlaser’s surface to identify DNA and single biological molecules. When DNA is attached to engineered nanoparticles, the micro-laser sensor can count each DNA molecule or even molecule fragments.