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标题: 日本研究人员发布true green laser diode!! [打印本页]

作者: laserfan 时间: 2009-7-28 13:38
标题: 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.

作者: laserfan 时间: 2009-7-28 13:42
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???

作者: trystar 时间: 2009-7-28 13:53
真是无奈，我国的半导体与欧美、日本相比差得太远了。

作者: 郁闷 时间: 2009-7-28 15:11
从最开始的材料就已经有很大的差距了
看来要加油了哦

作者: boague 时间: 2009-7-29 12:36
还有更多资料么？还有更多资料么？还有更多资料么？

作者: inter--diff 时间: 2009-7-29 13:34
怕什么，老共有的是外汇，全球贮备第一嘛！！！

作者: byrd_optics 时间: 2009-7-29 14:07
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……

作者: laserfan 时间: 2009-7-29 14:17
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?????

作者: laserfan 时间: 2009-7-29 14:19

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

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........."??

作者: kaka 时间: 2009-7-29 14:27
这种小科学技术不在中国战略的考虑范围内

作者: 再也不能这样 时间: 2009-7-29 15:09
能搞篇原文不？。。。。。。。。。。。。。

作者: laserfan 时间: 2009-7-29 15:20
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.

[Support documentation]
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.

作者: laserfan 时间: 2009-7-29 15:21
Green diode lasers a big breakthrough for laser-display tech
Japanese researchers demonstrate the missing link in laser display technology: true green diode lasers.
Applied Physics Express, 2009, DOI: 10.1143/APEX.2.082101

Ever wonder why projector systems and televisions doesn't use laser illumination? It isn't for safety reasons, and it isn't for efficiency reasons—laser diodes have efficiencies ranging from 30 to 50 percent. No, the problem is green light. We have red laser diodes, and blue laser diodes turned up nearly 15 years ago. But green—where the heck is the green laser diode?
A group of Japanese researchers have answered that question: in our lab. Yes, they have the first "true green" laser diode. It doesn't work that well yet but, based on past history, expect rapid progress from here and commercial laser diodes before the end of next year.
I guess the big question is "what took them so long?" And the answer to that question is a little bit complicated. First, lets take a look at "normal" lasers. The color of light generated by a normal laser, such as the red of a helium-neon laser or the blue-green of an Argon ion laser, is not under our control. Lasers require a rather special set of conditions to be met before they will work, and, nature only satisfies these with certain material/color combinations. This was, and continues to be, an immense source of frustration to scientists.
Laser diodes, which are made using the junction between two or more semiconductor materials, are slightly different. In this case, the color of the light is determined by the energy difference between the conducting electrons and the lowest available states in the nonconducting valence band. This gap can be adjusted by combining different materials and making sandwich structures, called quantum wells.
So, you end up with complicated materials, like alloys of aluminum, indium, gallium, and arsenide, combined with careful layering. One layer might have gallium, arsenide, and aluminum, while the next will have gallium, indium, and aluminum, and so on. To adjust the gap, one changes the ratios between the different components.
In principle, one can get any color, from blue right through to the mid-infrared, by combining the appropriate semiconductor materials. But the world had to wait about 20 years for the blue laser diode and another 15 years for green, so what went wrong?
Pooling indium and other difficulties
The general problem is that certain combinations of materials don't alloy very well. For instance, blue laser diodes use a gallium nitride system, and figuring out how to get nitride to mix through the gallium evenly turned out to be quite difficult. Green, it turns out, requires a high level of indium in certain layers of the quantum well structures. Unfortunately, the indium diffuses and pools together, and that messes up the whole structure.
The other problem is that gallium nitride has a natural electric field associated with it. Good gallium nitride substrates are typically grown in such a way that this field acts on electrons passing through the quantum well structures, preventing them from losing energy and emitting light. In other words, the electric field quenches emission in the blue-green and green part of the spectrum.
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.
Applied Physics Express, 2009, DOI: 10.1143/APEX.2.082101

作者: laserfan 时间: 2009-7-29 15:22
上面两个报道,够了吧?

国内做半导体行业的哥们努力奋斗!!!!!!!!!!!

作者: Nd:YAG 时间: 2009-7-29 22:11
国内目前的思维：
这东西好做不？——不好做
做出来的话稳定性怎么样？——不高，500小时
能不能很快的赚到钱？——有DPL532压着，一时半会赚不了。

——不做了！

作者: matthewlas 时间: 2009-7-30 11:18
不喜欢日本,郁闷中！！！！！！！！！！！！！！

作者: kaka 时间: 2009-7-30 11:58
还是国外的月亮圆,难怪国内好多牛人跑美国去了,国内难道全是白菜,希望楼主能研究出震惊世界的牛比半导体,为中国争光啊

作者: laserfan 时间: 2009-7-31 09:35

国内目前的思维：
这东西好做不？——不好做
做出来的话稳定性怎么样？——不高，500小时
能不能很快的赚到钱？——有DPL532压着，一时半会赚不了。

——不做了！
Nd:YAG 发表于 2009-7-29 22:11

还是应该多学习"科学发展观".....................

作者: laser.f 时间: 2009-7-31 10:29
中国激光器要发展，首先要出现一大批像cni这种做某些人眼里所谓的“低端”，但是能把小日子过滋润的企业。
不然没戏。
光是装逼是不顶用的。

作者: qyxhhl 时间: 2009-7-31 11:39
落后就要挨打。。。什么时候国内出个扛把子的啊。。。

作者: laserfan 时间: 2009-7-31 13:29

中国激光器要发展，首先要出现一大批像cni这种做某些人眼里所谓的“低端”，但是能把小日子过滋润的企业。
不然没戏。
光是装逼是不顶用的。
laser.f 发表于 2009-7-31 10:29

国内小企业当然做不了wafer类的工作.

但科学院,研究所,高校.........能否搞些突破??????????

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