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May 09

Interest in 2.0 micron Light is Growing

By JamesVanHowe CLEO Conference, CLEO Tech Transfer, CLEO: Expo No Comments »

Wavelength Modulation Spectrum using tunable 2.0 micron VCSEL; From JTh1L.6, A. Kahn et al,. "Open-Path Green House Gas Sensor for UAV Applications"

This post originally appeared on Jim’s Cleo Blog and is reproduced with permission of the author.

Today at CLEO I spent a large amount of time at the expo hunting down which companies were selling 2.0 micron wavelength products and why. In the technical program, there are a large number of contributed talks regarding 2.0 micron lasers, pulsed and continuous wave. On Monday I attended session CM1B, Ultrafast Mid-IR in which 5 out of 8 papers demonstrated ultrafast pulses about 2.0 microns. Today there was a session titled CTu2D, 1.5 to 5 micron Lasers which also had 5 talks out of 8 showing laser systems operating near 2.0 microns.

There have been and will be a handful of talks not pinned down to these topic categories as well:

-CM2B.2, “A Broadband 1850-nm 40-Gb/s Receiver Based on Four-Wave Mixing in Silicon Waveguides”

-CTu3M.7, “All-fiber 10-GHz Picosecond Pulse Generation at 1.9 microns without Mode-locking”

-JTh1L.6, “Open-Path Green House Gas Sensor for UAV Applications”

-CF1K.1, “Single-Frequency kHz-Linewidth 2-μm GaSb-Based Semiconductor Disk Lasers With Multiple-Watt Output Power”

-CF1N.4, “Double-wall carbon nanotube Q-switched and Mode-locked Two-micron Fiber Lasers”

However, what we like to research and what we can actually bring to market are often two very different things. I am therefore excited that it is not just 2.0 micron papers that are cropping up at this year’s conference, but 2.0 micron products at the expo as well.

So why is anyone interested in light in the 2.0 micron region? My personal interest stems from a research talk I saw by analytical chemist, Mark Arnold, at University of Iowa. Arnold is trying to perform some hard analytical  chemistry on 2.0 micron light shone through the skin on the back of one’s hand. He hopes that by looking at the absorption spectra, he can measure blood glucose levels without having to draw blood. This noninvasive testing would be a boon to diabetics who are not thrilled about pricking their fingers regularly. Wavelengths that are helpful for pinning down glucose, but that are not absorbed as readily by tissue are 2.13 microns, 2.27 microns, and 2.33 microns.In short, there are some interesting molecules around 2.0 microns on which to perform spectroscopy. For environmental sensing, there is 1877 nm, a well defined water absorption line, and 2004 nm, a good line for carbon dioxide detection, and many more.

Many of the companies I spoke with selling 2.0 micron components and sources confirmed such spectroscopic applications of their customers:

-Oz Optics now sells passive fiber components at 2.0 microns as well as DFB sources.

-Sacher Lasertchnik and Nanoplus make DFB lasers extending through the 2.0 micron region depending on your molecule of interest.

-Advalue Photonics makes thulium-based fiber laser systems and sells passive 2.0 micron products.

-New Focus will be developing tunable laser diodes about 2.0 microns in the next few months.

-Nufern and CorActive are selling Tm- and Ho-doped fiber for 2.0 micron amplification and for fiber sources.

-IPG sells a number of lasers from 2.0-2.8 microns based Cr:ZnSe as well as 2.0 micron fiber lasers using thulium doped fibers.

There are other advantages to 2.0 micron light as well… (for a list of more companies and the rest of the post, click here)

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May 07

Nanolasers are the rising stars

By Frank Kuo CLEO Conference, CLEO: Applications, QELS Conference No Comments »
Figure 1. The structure of a coaxial laser cavity. The enitre thing is ~ 500 nm in all dimensions. (b) and (c) shows the SEM images of two different structures. Courtesy of M. Khajavikhan et al. in Nature 482 204 (2012).
This post originally appeared on CLEO BLOG by Frank Kuo and is reproduced with permission from its author.

If you attend “QM1H • Spasers and Nanoemitters” today, you know exactly what I am talking about. Exciting new materials, including metamaterials, quantum wells, and quantum rods, are used for the realizations of the nanolasers. If you missed it (which is quite possible since there are many other outstanding technical sessions packed today), this short article is your second chance. Three examples of nanolasers are presented here (summarized from today’s speakers) to give you a taste of the flavors.

Nanoscale coaxial lasers:

This is a piece of artwork of nanofabrication. The researchers from UCSD are able to fabricate a nanoscale coaxial laser cavity on an InP substrate (figure 1). It is composed of a metallic rod with different coaxial disks. One of the disks, the gain medium shown in red, is made of 6 quantum wells (each one is made of Inx=0.734Ga1–xAsy=0.57P1–y/ Inx=0.56Ga1–xAsy=0.938P1–y, with an overall height of 200 nm). They are sandwiched between SiO2 and air plugs. With the help of these two plugs, the entire device behaves like a cavity which supports a few sparse EM like modes (figure 2). If you pump the device in a right way, you can excite these modes and build them up. The lower air plug also allows pump energy into the cavity and couples out the light generated in the coaxial resonator. So once you build up the modes, you can couple the light out. In other words, you can make this device lase.

The researchers pump this nanolaser with a 1064 nm laser and it will lase at 1.26 and 1.59 micron at room temperature depending on the overall structures of the nanodevice. I would like to have one of these as souvenir.

Figure 1. The structure of a coaxial laser cavity. The enitre thing is ~ 500 nm in all dimensions. (b) and (c) shows the SEM images of two different structures. Courtesy of M. Khajavikhan et al. in Nature 482 204 (2012).

Figure 2. The EM like plasmonic modes that can be supported by the cavity. Two different structures support different modes. Some of the modes can be pump and excited by 1064 nm laser. Courtesy of M. Khajavikhan et al. in Nature 482 204 (2012).

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May 06

Enjoy the local attractions while at CLEO: 2012

By admin Uncategorized No Comments »

The weather is going to be gorgeous this week in San Jose. So, if you have the opportunity to get out in between technical sessions or in the evening, be sure to take adavantage of some of the great area attractions and restaurants. The city of San Jose is so excited to have you visiting, they have arranged several Show Your Badge discounts specifically for CLEO attendees. Here are just a few of the venues you can visit and receive discounts up to 40%:

-Children’s Discovery Museum of San Jose
-San Jose Museum of Art
-Tech Musuem
-Loft Bar & Bistro
-Sonoma Chicken Coop
-Broadway San Jose

San Jose also has a Discover San Jose discount card that you can pick up at IEEE Photonics Society, APS and OSA booths and receive even more discounts at area restaurants and services.

Enjoy San Jose and the conference!

Apr 16

Trying to get a job? Try the online job fair at CLEO!

By Frank Kuo CLEO Conference, CLEO: Expo, Uncategorized 1 Comment »

This post originally appeared on CLEO BLOG by Frank Kuo and is reproduced with permission from its author.

There are many things you do not want to miss in CLEO: 2012– A conference full of high quality technical sessions spiced by cutting edge presentations from invited speakers, not to mention the inspirational talks of renowned plenary speakers. For young graduate students, these are stimuli they want to boost their research. On the other hand, in the mind of senior graduate students, there is one more mission besides getting loaded with technical knowledge – Landing on a job after graduation. The good news is that you can get two birds with one stone since CLEO provides a nice channel for you to get connected with your potential future employers.

If you are interested in staying in the academia, your advisor(s) and the department may be the best resources for you. However, if you consider changing the tracks and exploring the industrial career, CLEO: 2012 is something you cannot miss. It brings employers from the entire US under one roof, and you get to meet them all. This year, you can try the online job fair by CLEO and WORKinOPTICS by OSA to get a head start. Unfortunately, not all the employers are actively involved in the online job fair. As a result, walking throughout the exhibition hall will be your next move.

Trying to get exposed in the exhibition hall is a must. To get you exposed in a right way is not that straightforward. For the past few years, I feel lucky to have the opportunity to look into these job-hunting games from both sides (as a senior graduate student trying to impress future employers in the conference, and a employee actively working in the tradeshow). Here are some tips I hope that help:

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Mar 30

Highlights from the Program Chairs

By JamesVanHowe CLEO Conference, CLEO: Applications No Comments »

(One of seventeen youtube shorts from the program chairs highlighting hot topics for CLEO 2012)

This post originally appeared on Jim’s CLEO Blog and is reproduced with permission from the author.

For a few years now CLEO conference organizers have been posting youtube shorts highlighting contributed talks, symposia, research trends, and any new or unique directions for the upcoming conference. This year there are seventeen videos from the program chairs, all worth watching. However, for those who prefer text over A/V, I thought it might be helpful to highlight the highlights here.

Conference Program Stats

-The 2012 program has been selected from a record number of submissions.

-In just its second year, CLEO’s new Technology and Applications Conference saw a 50 % increase in submissions.

-350 papers, 15 % of all submissions, live in the subcommittee sections “Nano-optics and Plasmonics” or “Micro- and Nano-Photonic Devices”

-Subcommittee section: “Fiber Amplifiers, Lasers and Devices” was the single committee that received the most submissions

CLEO Applications and Technology: Government and National Science, Security and Standards Applications

In his youtube short, subcommittee Chair Ian Mckinnie of Lockheed Martin Coherent Technologies briefly discusses the two tracks of this subcommittee: 1) Ultrafast Laser Applications and 2) Instrumentation and Sensing.

Mckinnie talks about how the ultrafast program covers a broad range ultrafast laser applications spanning those performed at large facility-class systems to those on a bench top or operating table. These are exemplified by the tutorial talk, AW3J1, “Enabling Science at the Advanced Light Source X-ray Facility” that will be given by Roger Falcone of Lawrence Berkeley National Laboratory from 4:30-5:30 pm on May 9, and the invited talk AW3J4, “Applications of Ultrafast Lasers” by Mike Mielke of Raydiance Inc., also on May 9, but from 6:00-6:30 pm

The Advanced Light Source (ALS) is a large synchrotron source that produces laser light over an extremely broad spectrum including the hard-to-reach soft x-ray region. Falcone will be discussing the use of the coherent radiation at this user-facility for applications such as precise material processing and biomedical research.

On the other hand, Mielke will be discussing the use of compact fiber systems for micromachining and laser surgery. See blog post “Machining with Ultrafast Pulses” for some stunning videos and more information on these compact micromachining systems.

On the remote sensing side, Massayuki Fujita, from the Institute of for Laser Technology in Osaka, will be giving an invited talk on an application of remote sensing not typically found in the CLEO conference program- nondestructive inspection for heavy industrial processes. Fujita’s talk, ATuG3 “Nondestructive Inspection for Heavy Construction” can be heard on Tuesday May 8, at 2:30 pm.

CLEO Applications and Technology: Industrial Applications

In his video short, subcommittee chair Eric Mottay of Amplitude Systemes discuses the two major trends of the Industrial Applications subcommittee: 1) micro- and nanofabrication techniques and 2) applications of graphene.

Talks in the latter category can be found in a joint session with CLEO: Science and Innovation subcommittee six in session “Graphene and Carbon Advanced Photonic Materials” which will be held form 11:00am-1:00 pm on May 8. This session will host talks presenting graphene-based devices such as detectors, modulators, and tunable resonators. Recall that Andre Geim and Konstantin Novoselov were awarded the 2010 Nobel Prize for showing the “exceptional” properties of graphene such as it being simultaneously the thinnest and strongest material, having better electrical conductivity than copper, better heat conduction than all other known materials, and having nearly 100 % transparency yet an extremely high density (so dense helium atoms cannot pass through). Be sure to see how this “magical” material is being translated into devices that may be on the market in the next three to five years.

On the other hand, the invited talks for this subcommitee all center around micro- and nano- fabrication processes. Arnold Gillner of the Fraunhofer Institute will discuss how ultrafast lasers can be used for surface processing at the micro- and nanoscale level for applications in light guiding, fabrication of low friction surfaces, or wear-resistant surfaces. His talk, ATu3L1, “Micromanufacturing and nano surface functionalisation with ultrashort pulsed lasers” is scheduled for May 8, at 4:30 pm. Additionally, Paul Webster from Queen’s University will be discussing online monitoring during fabrication, particularly concerning the control of depth, in invited talk ATu3L5, “Inline Coherent Imaging: Measuring and Controlling Depth in Industrial Laser Processes,” on May 8, at 5:45 pm and Rick Russo from Lawrence Berkeley National Laboratory will be speaking about real-time spectroscopy of a sample after it has been turned into a plasma through laser ablation in talk, AW1H3 “Laser Plasmas for Spectrochemistry” on May 9, at 11:00 am.

CLEO Applications and Technology: Energy and Environment

In his video short, subcommittee chair Christian Wetzel from Rensselaer Polytechnich Institute discusses two trends… click here to read the full original post

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Mar 26

Recording the data at the “ultrasfast” rate for your digital device.

By Frank Kuo CLEO Conference, CLEO: Applications, Uncategorized No Comments »

This post originally appeared on CLEO BLOG by Frank Kuo and is reproduced with permission from its author.

Figure 1. A generic ferrimagnet, composed of Fe and Gd, shows the alignment of magnetic moment. Courtesy of I.Radu et al., Nature 472 205 (2011).

The principle of magnetic storage used by most hard drives is an important pillar in the evolution of modern digital world. Before the advent of flash memory, it dominated the way we saved our data. Simply speaking, binary information (0 or 1) is presented by small magnets pointing forward (0) or backward (1); let’s say the north is the head. Writing the data is by changing the pointing directions of these magnets, usually fulfilled by an electric coiled wrapped head (by applying the current into the head, you create a strong external magnetic field that realign the directions of the small magnets in the hard drive, one at a time). In addition, packing in as many magnets as possible in a limited volume will define the capacity of a hard drive, and this is improving ever since the first device available. Imaging the first computer I had came with a hard drive of 400 MB, and now a decent one has a few TB storage capacities. By comparing the number, you can realize how much effort and advances in the business of data storage. For a very nice introduction, you can find at hard drive 101: magnetic storage.

A nice paper where ultrafast laser pulses (sub 100 fs) instead of external magnetic field are used to write data intrigued my curiosity. I know immediately that it is the heating effect that causes the change of the magnetization of the small magnets in the hard drive. But for me, the heat has no directionality, how it can tell the magnet to point forward or backward. It should just erase the information since an ultrafast laser pulse can easily create a hot environment above Curie temperature where the magnetization is destroyed. So in my mind, an ultrafast laser is a hard drive terminator, not a hard drive writer. Driven by this curiosity, I dug in to find out, and this is how:

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Feb 28

Semiconductor Laser’s Golden Anniversary

By JamesVanHowe CLEO Conference No Comments »

First room temp. CW semiconductor nanolaser with subwavelngth cavity, presented at CLEO 2011. From K. Ding et al, CTuG2, CLEO 2011.

This post originally appeared on Jim’s CLEO Blog and is reproduced with permission from the author.

The year 2012 marks the impressive 50th anniversary of the invention of the prolific and ubiquitous semiconductor laser. Almost every household in the industrialized world owns at least one, be it in a DVD player (maybe two if it is a Blue-ray), CD player, optical mouse or depend on them indirectly for long-distance phone service, digital cable, or internet access. Besides making telecommunications a practical possibility, semiconductor lasers have paved the way for the development of silicon photonics and will be pivotal in the future of optical information storage and processing. Despite their primary use in mass consumer markets for communications, information processing, mutimedia, and teasing cats (you can even get semiconductor laser pointers with phase masks and lens attachments that project images mice or fish on the floor for your feline to chase), many subfields have profited from the low-cost and small-footprint of these robust laser sources. Take for example the handful of semiconductor sources offered commercially by Thorlabs for optical coherence tomography, or the inexpensive semiconductor laser diode sources used by the Ozcan group for field-portable, ultra-low footprint, holographic microscopes.

There are too many other technologies and subfields to name that have profited as well. All you need to do is think of the numerous optics applications that live at telecom wavelengths near 1300 nm or 1550 nm or DVD player wavelengths, 405 nm and 635 nm. Such lasers offer unbelievable device characteristics at such a low price that researchers and venture capitalists often build their technologies to fit these wavelengths instead of the other way around.

Amnon Yariv and Pochi Yeh write in their 2007 edition of the book Photonics that,

“The semiconductor laser invented in 1961 is the first laser to make the transition from a research topic and specialized applications to the mass consumer market…It is by economic standards and the degree of its applications, the most important of all lasers.”

To celebrate the most important laser of lasers, CLEO will be hosting a special symposium with talks from pioneers of semiconductor laser technology. The list of speakers and subjects has been well-crafted to paint not only a historical picture but to address current research and trends on this ever-evolving technology.

From a fundamentals perspective Russel Dupuis from Georgia Tech will be talking about device materials. Nobel Laureate Herbert Kroemer of University of California Santa Barbara will discuss the double heterostructure which is still the basic framework for almost all semiconductor light sources and solar cells and which without there would be no continuous wave (CW) lasing in semiconductor devices at room temperature. To this end, Morton Panish, formerly of Bell Laboratories, will describe the development of the first room temperature semiconductor laser.

Evolution of threshold current. From Nobel Laureate Z. Alferov, IEEE J. Sel. Top. Quant. Elec. 6, 832, 2000.

Charles Henry, formerly of Bell Laboratories, will discuss the quantum well structure which was pivotal in reducing active layer thickness and therefore significantly reducing threshold current, see the figure above. Yasuhiko Arakawa from the University of Tokyo will discuss quantum dot lasers which reduced threshold densities even further and remains a developing area of semiconductor laser physics research.

On the more practical side, Jack Jewell, of Green VCSEL will discuss the vertical cavity surface emitting laser (VCSEL) which among other important device attributes may be the best laser for high-yield production. VCSELs are grown, processed, and tested in wafer-form allowing parallel fabrication and testing, minimizing labor and maximizing yield. They also take up less space on a wafer- about three times less than edge emitters of similar power and can be made in 2-D arrays. Jewell will likely discuss the benefits of lower power consumption of VCSELs for use in short-reach, high-speed networks. My understanding is that the “green” in “Green VCSEL” refers to environmental considerations not wavelength.

There will also be talks discussing the semiconductor laser’s role in telecommunications, integrated and hybrid optical circuits, quantum cascade lasers , high-power devices, as well progress in nano laser structures with subwavelength volume (see the figure at the top).

Whether to learn the history, fundamental principles, pay homage to the pioneers, or to learn new trends, be sure to mark your calendar for the 50th Anniversary of the Semiconductor Laser symposium to celebrate “the most important of all lasers.”

For the full original post, click here.

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Jan 27

Why a Temporal-Cloak is so Great: Uncovering the Hype

By JamesVanHowe Uncategorized No Comments »

From R. Boyd and Z. Shi,"News and Views" Nature, Jan 5, 2012, explaining temporal-cloaking

This post originally appeared on Jim’s CLEO Blog and is reproduced with permission from the author.

At Frontiers in Optics 2011 just this last October, Moti Fridman from Alex Gaeta’s group presented work on a the first experimental demonstration of temporal-cloaking using a time-lens system. The work was based upon a theoretical paper from Martin McCall et al in the February issue of the Journal of Optics, and at the beginning of this month, appeared in an in-depth treatment in the January 5, issue of Nature. Besides the usual barrage of bloggers latching onto science-fictionesque results of new research, time-cloaking was also written up in traditional news media such as the Christian Science Monitor.

Temporal-cloaking certainly sounds like something out of Star Trek, but what is it and why is it so great? What makes a temporal cloak truly exciting, and what a majority of the recent articles and posts fail to highlight, is that the temporal-cloak allows cloaking over an infinite section of space albeit for a finite duration of time.

Let’s imagine Harry Potter and his invisibility cloak. If the invisibility cloak is a temporal-cloak, Harry can move as far as he wants to the left-and-right and up-and-down without being seen for duration of the cloaking window. Harry can also move a little bit forward and backward without being seen, but not much or else he will walk out of the cloaking time-window (which is 50 ps for the Gaeta group’s work or about 1.0 cm in fiber). It is crucial that he is in the right place in the axial dimension (forward/backward) since the window occurs at a specific place in space, but he has total freedom in the transverse dimension for the duration of the cloak. Conceivably Harry could pull-off a bank robbery as long as the bank and the vault are inside that particular infinite pancake of cloaking window and within the duration of the window.

Contrast that to a spatial cloak which gives cloaking for an infinite amount of time, but only a finite section of space. If Harry has a spatial invisibility cloak, then he can stand in one spot for as long as he wants without being seen.

Finally, if Harry has a spatio-temporal cloak, conceivably he can maintain invisibility for any duration of time and throughout any volume of space.

The temporal-cloak shown by the Gaeta group is not a practical cloak. If you scrutinize the setup you’ll find that the way that they detect a cloaked event is through lack of nonlinear mixing. A nonlinear signal tells them the event is detected, and no signal tells them that the event is cloaked. You could just turn the power down to get the same result. They also couple into and out of the cloaking window with fiber-couplers between the cloaking apparatus. You can’t send both the signal and the event to be cloaked down the same fiber because if the “event” goes through the same time-lens system as the “signal” the event will appear superposed instead of cloaked. Basically they had to sneak it into the right spot at the right time along a different path of propagation.

However, the point of the work was not to show practical temporal cloaking for masking or encryption, but to show the very odd, very fundamental, and very cool phenomena of creating and tailoring gaps in time. So even if the temporal-cloak won’t be used anytime in the near future for cracking safes, it does bring the optics community closer to a true spatio-temporal invisibility cloak. It might be time to start brushing up on the rules of Quidditch.

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Jan 09

The world’s smallest Stirling engine is powered by laser!

By Frank Kuo CLEO Conference, CLEO: Applications, Uncategorized No Comments »

This post originally appeared on CLEO BLOG by Frank Kuo and is reproduced with permission from its author.

Figure 1. The realization of the microscopic Stirling engine. Courtesy of V. Blickle and C. Bechinger in Nature Physics doi:10.1038/nphys2163 (2011).

When people mention the word “laser” to you, what is the first thing coming to your mind? Most of us associate lasers to their scary and destructive power, just like how we are educated in the Star Wars movie series. In reality, lasers can be quite gentle and perform very accurate and precise assignments, like micro-machining (Jim has a nice article about it). In fact, laser can be so gentle that researchers have used it to power the world’s smallest Stirling engine, which is composed of single tiny melamine bead (~ 3 um in diameter) in the water bath.

To realize how this ingenious microscopic engine works, we have to step into the phenomenon of optical trapping/tweezers first. Thanks to the detailed illustration on wiki, I can just summarize it in a few sentences — When the laser is tightly focused, or when it has the Gaussian beam intensity distribution, the tiny particle will be trapped in the focus or the center of the Gaussian beam, just like being trapped in a potential well. This is a result of momentum conservation. When the refracted light rays exit the particle, they exert momentum kicks to the particle, and the net result of these kicks is a force that traps the particle at the center of the focus. If the particle is in the focus, this force is zero. If the particle drifts away from the center, the kicks will be imbalanced and a net force will pull it back to the center. This particle behaves exactly like it is in a potential well. The steepness of the well depends on the laser intensity as you might guess it already. And our talented researchers use this technique to power the microscopic engine.

Here is how it goes. Figure 1 shows the comparison of a microscopic Stirling engine with a macroscopic one. As shown in step (1), the bead is trapped in a potential well by a focused laser beam. From step (1) to (2), the laser intensity is increased such that the bead would be confined in a smaller volume due to the steeper potential well. This is similar to moving a piston to squeeze the volume in the chamber. From (2) to (3), the water bath is heated by another NIR laser, and this step is similar to heating a macroscopic chamber. From step (3) to (4), the potential well is relaxed and the work is exerted from the bead to the surrounding, just like in macroscopic world, the gas is pushing the piston to exert work for useful application. From (4) to (1), the NIR laser is turned off, and the bead is cooled down, just like in the traditional Stirling engine, the gas is cooled back to the ambient temperature. Smart and elegant design, isn’t it?

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Dec 13

Machining with Ultrafast Pulses

By JamesVanHowe CLEO: Applications No Comments »

(From Raydiance Inc)

This post originally appeared on Jim’s CLEO Blog and is reproduced with permission from the author.

As someone who has been trying to design novel ultrafast laser systems for the past eight years, my eyes were drawn to the title “Applications of Ultrafast Lasers” of Dr. Mike Mielke’s talk from Raydiance Inc. from the awesomely overwhelming list of invited speakers at CLEO 2012. Dr. Mielke’s talk is one of a handful in CLEO’s new Application and Technology conference which debuted last year in Baltimore in order to better bridge the gap between fundamental research and product commercialization.

To see what background information I could potentially find, I went to Raydiance’s website to find a wealth of information on micromachining and a host of video shorts of ultrafast laser micromachining in action. They are so pleasing to watch, I couldn’t help embedding many of them in this post.

Micromachinging with ultrafast lasers allows the removal of material without the introduction of heat (see the video above of laser micromachining on a match head without it igniting). Ultrafast lasers therefore give the advantages of laser machining- tailoring submicron features on the workpiece, without thermal collateral damage. For example, if you are going to have your dentist drill a tiny hole in one of your teeth (see the figure below) , you’d rather have her use the 350 fs laser shown in b) rather than 1.4 ns laser in a) in which the heat generated damages and fractures the tooth.

Drilling tooth enamel with a) 1.4 ns 30 J/cm2 laser pulses and b) with 350 fs 3 J/cm2 pulses. From B.C. Stuart et al, LLNL

This is because drilling with the femtosecond pulses relies on an entirely different physical process for removal of material than nanosecond pulses. For long pulses (> 100 ps), photons are absorbed by the material and converted into heat. This eventually fractures, melts, or vaporizes material at (and nearby) the laser focus. On the other hand, if the pulse is fast enough (< 1 ps), the material is removed solely by photo-ionization. Rather than dumping energy into the material, electrons of target molecules are stripped off by the intense electric field of the pulse. No absorption takes place and therefore no heat is generated.

Because the mechanism for material removal using ultrafast pulses does not depend on the material properties as it does for thermal ablation, such as the melting point, conceivably any material can be machined using ultrafast pulses. This has allowed Raydiance to micromachine polymeric materials for manufacturing next-generation vascular stents and microfluidic devices (see the videos below).

(From Raydiance Inc)……..for the full original post click here.

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