CdTe/CdS量子点实现绿色被动Q开关激光：最高33.6mW输出

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本文是一篇邀请论文，聚焦于光子学领域的前沿进展——被动式Q开关操作在绿色激光中的应用。在过去，这种技术对于绿色波长（522纳米）的直接产生研究相当罕见。作者团队由厦门大学电子工程系的研究者们主导，他们利用CdTe/CdS量子点作为非线性吸收介质，成功实现了Praseodymium掺杂的Yttrium Lithium Fluoride (YLF)绿光激光器的被动式Q开关工作模式。研究中，通过CdTe/CdS量子点的独特光学特性，实现了对激光脉冲的调制，从而实现高效率的光脉冲控制。在实验条件下，研究人员达到了最高平均输出功率33.6毫瓦，这是在840纳秒的最短脉宽下实现的。这意味着单个脉冲的能量达到了0.18微焦耳，峰值功率则达到了0.21瓦特。这些结果表明，量子点材料在绿色波长激光器的Q开关应用中具有潜在的优势，可能为绿色光通信、光存储以及其他需要高精度短脉冲的应用提供了一种新颖且高效的解决方案。这项工作的创新之处在于它填补了绿色波长被动式Q开关激光技术的空白，展示了量子点材料在激光技术中的新用途。此外，通过优化量子点的制备和集成方法，未来有可能进一步提升激光器的性能，包括更高的平均输出功率、更短的脉宽以及更稳定的Q开关效果。这篇论文为绿色激光器的未来发展指明了一个新的方向，即利用量子点的非线性光学性质来增强其动态控制能力。这不仅有助于推动激光技术的革新，也有望在诸多领域如生物医学成像、精密加工和材料处理等方面开启新的应用可能性。通过深入研究和优化，这种基于量子点的绿色Q开关激光技术有可能成为激光科学的一个重要里程碑。

Passively Q-switched green laser operation using

CdTe/CdS quantum dots

(Invited Paper)

Xigun Yan (严希滚)

1,3

, Saiyu Luo (罗塞雨)

, Bin Xu (徐斌)

*, Huiying Xu (许惠英)

Zhiping Cai (蔡志平)

, Jingzhou Li (李京周)

, Hongxing Dong (董红星)

Long Zhang (张龙)

, and Zhengqian Luo (罗正钱)

1,3,

Department of Electronic Engineering, Xiamen University, Xiamen 361005, China

Key Laboratory of Materials for High-Power Laser, Shanghai Institute of Optics and Fine Mechanics,

Chinese Academy of Science, Shanghai 201800, China

Shenzhen Research Institute of Xiamen University, Shenzhen 518057, China

*Corresponding author: xubin@xmu.edu.cn; **corresponding author: zqluo@xmu.edu.cn

Received September 22, 2017; accepted November 10, 2017; posted online December 26, 2017

The direct generation of passively Q-switched lasers at a green wavelength has rarely been investigated in the

past. In this Letter, we demonstrate a passively Q-switched praseodymium-doped yttrium lithium fluoride green

laser at 522 nm using CdTe/CdS quantum dots as a saturable absorber. A maximum average output power of

33.6 mW is achieved with the shortest pulse width of 840 ns. The corresponding pulse energy and peak power

reached 0.18 μJ and 0.21 W, respectively. To the best of our knowledge, this is the first demonstration in regard

to a quantum dots saturable absorber operating in the green spectral region.

OCIS codes: 140.3480, 140.3540, 140.3580.

doi: 10.3788/COL201816.020005.

Passive Q-switching and mode locking are two crucial

technologies for short and ultrashort pulse generation.

Based on these two technologies, efficient, reliable, and

cost-effective saturable absorbers are always desirab le.

If the saturable absorber is also universal for laser opera-

tion with large wavelength range, it would be the desired

candidate for researchers. Most conventional saturable

absorbers, like Cr

4þ

-, V

3þ

-, Co

2þ

-, and Cr

2þ

-doped mate-

rials

[1–6]

, as well as the well-known semiconductor saturable

absorber mirror (SESAM)

[7–9]

, cannot nicely match all

these wanted merits.

During the past decade, a kind of new s aturable

absorber on the basis of various nanomaterials has been

greatly developed. Mostly, these nanomaterial’ssatu-

rable absorbers exhibit some advantages, including

broadband saturable absorption, low cost, and easy fab-

rication. These advantages are indeed not covered for the

conventional saturable absorbers. As a consequence, be-

cause of these desirable advantages, nanomaterials used

for saturable absorbers have become an increasingly

popular research topic, and relevant studies have

involved Q-switched and mode-locked laser operation

from visible to midd le inf rared

[10–26]

, such as carbon nano-

tube

[10–12]

and other two-dimensional (2D) nanomaterials

like graphene

[13–15]

, topological insulators (TIs)

[16–20]

transition metal dichalcogenides (TMDCs)

[21–27]

,black

phosphorus

[28– 30]

,etc.Especially,atpresent,noconven-

tional saturable absorbers as mentioned above, i.e.,

SESAM, Cr

4þ

-, V

3þ

-, Co

2þ

-, and Cr

2þ

-doped materials,

have been reported to be a Q-switcher or mode locker for

green laser emission. Recently, a green laser at 522 nm

has been successfully Q-switched and mode-locked using

MoS

[21,22]

On the other hand, quantum dots (QDs) used as satu-

rable absorbers have also attracted attention recently be-

cause of their relatively broadband absorption spectrum,

arising from inhomogeneous broadening associated with a

variation of dot sizes

[31]

. A main advantage of QDs over

those 2D nanomaterials is that, because of high-level con-

trollability over the size of the crystals, it is possible to

have very precise control over the conductive properties

of the material. The smaller the size of the crystal and

the larger the band gap, the greater the difference in en-

ergy between the highest valence band and the lowest con-

duction band becomes. Although the energy band gap of

the 2D nanomaterials can also be tuned by increasing their

number of layers, the multilayer 2D nanomaterials will

transform into indirect semiconductors, which will lead

to a greatly reduced electron transition rate. As a result,

it results in large saturable intensities for 2D nanomateri-

als saturable absorbers

[32]

. Additionally, compared to their

quantum well counterparts, QDs could, in principle, offer

lower saturation fluence, faster recovery time, and lower

non-saturable losses

[32,33]

. Recently, using QDs as saturable

absorber, we operated passively Q-switched visible lasers

at 721, 640, and 607 nm

[34].

In this work, core/shell structure QDs, CdTe/CdS, were

fabricated by a liquid-phase method, which provides a

much less expensive and far simpler alternative to epitax-

ially grown semiconductors. The core/shell materials of

CdTe/CdS QDs have the same lattice structure and exhibit

a small lattice mismatch, which caused the QDs to have a

COL 16(2), 020005(2018) CHINESE OPTICS LETTERS February 10, 2018

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CdTe/CdS量子点实现绿色被动Q开关激光：最高33.6mW输出

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