日本研究人员发布true green laser diode!!
据Applied Physics Express, 2009, DOI: 10.1143/APEX.2.082101消息:Japanese researchers demonstrate the technology: true green diode lasers.
以下是部分摘要:
The new researchers, from Semiconductor Technologies R&D Laboratories at Sumitomo Electric Industries, got around the electric field problem by changing the orientation of the gallium nitride substrate. That is a story in itself, but, briefly, they found an appropriate template that encouraged the gallium nitride to grow so that it presents a different surface to the world, one that is electrically neutral. On to this, they grew the various layers required for a green laser diode. However, what they don't tell us is how they prevented the indium from diffusing. I would guess that the orientation of the substrate somehow slows the diffusion down.
In any case, the structure worked. They report laser emission for colors between 520 and 531nm, which is pretty much dead center on the green color required for display technology.
Of course, the laser wasn't very good: it was operated in pulsed mode (all lasers operate in pulsed mode when they are first switched on). The efficiency was also shockingly bad at 0.1 percent, mostly due to the pulsed nature—if we ignore the off time, the efficiency goes up to about 20 percent. The authors observe that the electrical contacts weren't optimized, leading to high resistive losses; the laser operated at about 20V, while a normal laser diode operates between 1 and 3V.
You can guarantee that those problems will be solved pretty quickly now that the researchers know they are on the right track. Once volume production starts, prices will fall into line with red and blue laser diodes, and then the cost of projection display systems should fall dramatically. In the end, what many researchers are aiming for are hand-held projection display systems.
For those of you wondering why green laser pointers exist, here is the short answer: take an infrared diode laser, use it to power another laser that is deep into the infrared. Use an optical nonlinear crystal to double the frequency and half the wavelength of that laser. You get 530nm light and profit from a complicated little device. The overall efficiency of this process, however, is something like 6 percent. 哎,蓝光LD让日本大赚了一笔,
因为近年蓝光光盘标准要普及了!!!!!
看来绿光LD又要让日本大赚一笔,
未来的laser projector, laser TV.....都将成为现实.
我国搞半导体激光器(生长\工艺\封装...)的科学家们,感想如何??? 真是无奈，我国的半导体与欧美、日本相比差得太远了。 从最开始的材料就已经有很大的差距了
看来要加油了哦 还有更多资料么？还有更多资料么？还有更多资料么？ 怕什么，老共有的是外汇，全球贮备第一嘛！！！ 这不是“生长\工艺\封装”的问题，而是基础科研的问题，基础的芯片才是技术的关键，是芯片的科研能力上不去，在半导体这一块中国就只能是“生长\工艺\封装”，真的有点悲哀…… 据说国内很多研究所和高校都有MOVCD, MBE....花很多银子买的,
做个wafer咋就这么难哪????? 这不是“生长\工艺\封装”的问题，而是基础科研的问题，基础的芯片才是技术的关键，是芯片的科研能力上不去，在半导体这一块中国就只能是“生长\工艺\封装”，真的有点悲哀……
byrd_optics 发表于 2009-7-29 14:07 static/image/common/back.gif
看来我们大家要讨论一下"中国有没有真正做半导体的科学家了?是不是把国外芯片买来一package就水自己作出半导体激光器的........."?? 这种小科学技术不在中国战略的考虑范围内 能搞篇原文不？。。。。。。。。。。。。。 Sumitomo Electric Develops The World’s First Pure Green Semiconductor Laser
- A Newly Developed Gallium Nitride Crystal Leads To The Achievement -
July 16, 2009
Sumitomo Electric Industries, Ltd.
Sumitomo Electric Industries, Ltd. has successfully developed the world’s first green laser diode lasing at 531 nm.
Light sources using lasers for display applications, such as laser TV’s and pocket laser projectors, are expected to have superior properties in terms of size, weight and power consumption. For this reason, R&D activities aimed at commercialization of these devices have expanded rapidly over the past several years. Up to now, only red and blue laser diodes were commercially available, while green lasers (*1) were obtained by frequency conversion of infrared lasers. Gallium nitride (GaN) semiconductors, commercially available for blue LEDs, are also expected to be the key material for light-emitting devices in the green region. However, the material has been plagued with a phenomenon where the luminance efficiency shows a rapid decline with increasing wavelength.
At Sumitomo Electric, we have overcome this problem by developing a GaN crystal which inhibits the efficiency drop, resulting in room temperature pulse operation of a laser diode emitting in the pure-green region at 531nm. It is the first green laser diode in the world.
Some of the features of our green laser diode are as follows.
1 High quality crystal emitting in the green region
The luminous efficiency of GaN light-emitting devices is known to show a sharp decline with increasing wavelength (*2). This is a combined result of the internal field effects as well as the deterioration of the crystal quality of the active layer. Several organizations are studying to alleviate this problem by changing the crystal orientation.
At Sumitomo Electric, we have developed a crystal which weakens the internal field effects and also improves the quality of the active layer. This has lead to the successful development of the world’s first green laser diode.
2 Tunability of the wavelength in the green region
With a proper design of the active layer, we have succeeded in covering the entire range of the lasing spectrum in the green region. While the lasing wavelengths of the conventional frequency-converted lasers are locked at a specific wavelength, our device can be tuned to any wavelength in the green region. Furthermore, the lasing spectrum remains virtually unshifted even in the high current range, and therefore, we believe our device has advantages in high power applications.
Another advantage of our green laser diode is that the dependence of wavelength at ambient temperature is minimal.
We have applied for over 60 patents related to this technology. Details of the device will be presented in the July 17th edition of the Applied Physics Express.
The successful development of the green laser diode leads to the red-green-blue (RGB) laser light sources and should lead to new applications. We will continue to seek new business opportunities utilizing our nitride semiconductor technology.
Photo 1. Green laser emitting from an oscillator below right
※1 Green laser
A laser operates in the green region of the optical spectrum. Until now, green lasers based on semiconductors materials, such as blue or red lasers, did not exist. Commercial green lasers, such as those used in laser pointers, emit green light at the wavelength of 532nm by down converting a 1064nm infrared laser light. The needs for large number of mechanical parts resulting in high costs, along with their inherent low efficiencies, have prevented widespread commercialization of these devices.
※2 Sharp efficiency decline with increasing wavelength
The main reason for the low luminous efficiency of green light-emitting devices based on GaN materials is an electric field, commonly known as “the piezoelectric field.” Piezoelectric polarization caused by a large distortion in the crystal structure is the origin of this field. The piezoelectric field, while it has less effect on blue lasers, has a serious influence upon green lasers.
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