Femtosecond Lasers

What is a Femtosecond Laser?

A Femtosecond laser (fs laser or fs pulsed laser) is a laser which emits optical pulses with a duration below 1 picosecond. A femtosecond (fs) is one quadrillionth of a second or 10⁻¹⁵ seconds. Femtosecond pulses are generated through a process known as mode-locking. Mode-locked lasers utilize phase locking to interfere a large number of lasing modes together in such a way as to cause the generation of ultrafast pulses.

As a result of having such short pulse widths, femtosecond lasers have incredibly high peak powers typically in the MW to GW range. At a given pulse energy, the peak power of the laser increases as the pulse width gets shorter. Therefore, femtosecond lasers have much higher peak power than longer pulsed picosecond, nanosecond, or millisecond pulsed lasers. These higher peak powers result in higher removal rates, for example, in a given material due to the fact that more of the total energy is transferred to the material and less is pulled into heating the material.

The high peak powers of these femtosecond lasers, often several MW, creates a breakdown between the electrons and atoms in the material, causing what is known as a “Coulomb explosion”. A Coulomb explosion is a cold processing alternative to the conventional thermal ablation utilized by longer pulsed lasers. Ablation is a thermal process that relies on local heating, melting, and vaporization of molecules and atoms. Ablation can be detrimental for some laser applications as it typically creates unwanted HAZ, recast and burs, all of which are negative effects of heat, making cold ablation a better option for certain applications.

Pulsed Lasers that produce less than 10 picoseconds pulses (e.g. femtosecond lasers) belong to the category of Ultrafast Lasers or Ultrashort Pulse Lasers, even though they may still be called picosecond lasers. Ultrafast Lasers are ideal for the non-thermal or cold ablation of any material, including metals, ceramics, polymers, composites, coatings, glass, plastics, diamonds, and PET. Ultrafast lasers can even operate on layered substrates. Cold ablation allows for material to be removed with high precision and without heating the residual matter. Thus, femtosecond fiber lasers will not produce heat affected zones, splatter, or significant recast. Additionally, these lasers will eliminate the need for any post-processing.

In recent years, femtosecond fiber-based lasers have started to replace older, bulkier Ti:Sapphire lasers. Femtosecond laser prices are much lower when compared to the ti sapphire laser price. Total cost of ownership and maintenance time and cost are also lower with air-cooled fiber lasers when compared to water-cooled Ti:Sapphire laser systems. The Alcor laser platform is a great contender for replacing these legacy laser sources. These ultrafast fiber lasers also allow you to place the controller in a rack mount, for example, while positioning the smaller laser head where you need it.

Our Femtosecond Laser Products

RPMC lasers offers a wide range of high quality femtosecond pulsed lasers designed with repetition rates ranging from single shot up to 80 MHz, ultrashort pulse durations from 150 up to 900 femtoseconds, and various pulse energy specifications depending on the configuration.

Our femtosecond lasers are available in 515 nm, 532 nm, 920nm, 1030 nm, 1035 nm, 1064 nm, and 1300 nm wavelengths, with average power up to 30 W available. We supply diode-pumped solid-state (DPSS) lasers, fiber lasers, and DPSS amplifiers in our femtosecond laser category.

At one-tenth the volume, twice the power, and half the cost, our fs Fiber Lasers are perfect replacements for old, outdated Ti:Sapphire lasers. With useful wavelengths like 920, 1040, and 1064nm, you aren’t paying extra for unnecessary wavelength tunability. With a compact, air-cooled, maintenance-free design, and an industry-standard beam height, you’ll see a fast ROI with less downtime and more room to breathe after easily dropping one of these plug-and-play fs Fiber Lasers into your old Ti:Sapphire laser footprint.

Our Femtosecond Laser Experience

RPMC is your Femtosecond Laser Supplier! We have supplied many fiber-based femtosecond laser systems to various researchers, laboratories, and materials science development teams around the country. Often, the researchers we work with don’t have extensive laser experience, and rely on us to help them choose the best laser for their application or project.

Deeper Dive into Femtosecond Lasers

Femtosecond Laser Applications

The high peak power, high energy pulses, and short pulse widths of femtosecond lasers are ideal for a wide range of applications especially for multi-photon microscopy, non-linear spectroscopy, second harmonic generation (SHG), and micromachining.

Higher Power fs Fiber Lasers to Image Better, Deeper & Faster

How Laser Parameters Define Optimal Results in Multiphoton Excitation Fluorescence

Two-Photon Microscopy: Technique of Choice for In-Vivo High-Resolution Imaging

Two-photon microscopy has become a key fluorescent imaging technique that enables in-vivo, non-invasive 3-dimensional imaging with sub-micron resolution in volume. Challenged by the wider variety of applications particularly in the field of neuroscience, two-photon microscopy has led to the conception of systems using new excitation techniques and innovative laser sources.

Why femtosecond lasers?

Multiphoton excitation needs high peak power and femtosecond lasers have emerged as the optimal solution due to their relatively low fluence limiting damages to living samples. Wavelength tunable Ti:Sapphire lasers met this requirement and have been extensively employed in Biophotonics. This led to standard methods using a conventional pulse regime with typically 100-150 fs pulse duration, 80 MHz repetition rate and watt level average power with specific wavelengths such as 800 nm, 920 nm and 1040-1080 nm.

A variety of pulse characteristics with novel femtosecond lasers

Recent technological developments led to the commercial availability of new generations of femtosecond lasers capable of offering a wider variety of pulse regimes. Femtosecond lasers based on Optical Parametric Chirped-Pulse Amplifications (OPCPA) offer the widest range of pulse regimes, capable of operating at low and selectable repetition rates, in the µJ level and covering a wide wavelength range from near infrared to infrared wavelengths. Although OPCPA based systems offer high versatility, they are bulky, expensive, not as reliable and stable as conventional lasers.

Alternatively fixed wavelength femtosecond lasers have proved to offer a good compromise for 2-photon excitation microscopy. Their main advantages reside in its low price, very compact and robust format, high electrical efficiency and high reliability. This novel generation of lasers available at 780 nm, 920 nm and in the 1030-1070 nm wavelength range were initially conceived to match standard pulse regimes of Ti:Sapphire lasers to replace or complete this solution. Fixed wavelength femtosecond lasers are now offering alternative pulse regimes not accessible by Ti:Sapphire lasers such as various repetition rates, higher average power and higher energy making them ideal candidates to push boundaries of today’s research. Nevertheless, with such a wide variety of femtosecond lasers, choosing an adequate laser solution suitable for a given application is becoming challenging.

Laser parameters for multiphoton excitation

In the following, we review how laser pulse characteristics affect multiphoton excitation processes.

Multiphoton excitation microscopy relies on nonlinear optical processes produced in living samples, generating localized fluorescence which will be selectively detected to produce an image. Optical nonlinearities are directly related to laser pulse properties as high light intensity is required to enhance nonlinear effects in samples, here biological materials.

High intensity is achieved by focusing a laser beam to spot size in the µm range. The challenge is to obtain multiphoton excitation fluorescence deep into a sample where water absorption and scattering are significant. While it is well known that the capacity to focus is given by low aberration, high numerical aperture microscope objectives combined with adequate laser beam dimensions, the choice of excitation wavelength is also important as shorter wavelength would result in higher scattering loss. Water absorption must also be considered to image deeper into a biological sample. Assuming that all spatial and spectral characteristics of a laser beam are maintained and optimized, one need to consider actual pulse regime to maximize multiphoton excitation efficiency.

Pulse parameters for multiphoton excitation

Once nonlinear fluorescence is produced by a tightly focused laser beam, laser pulse parameters must be optimized for further enhancement. Considering only pulse characteristics, multiphoton excitation fluorescence $F$ directly depends on average power $Pav$ and peak power $Ppk$ :

$F\cong(Pav*Ppk)$

Basically, fluorescence is proportional to average power for a given peak power. Peak power is related to pulse duration $\tau$ and pulse energy $E$ by:

$Ppk=E/\tau$

This means that, for a given pulse energy, shorter pulse duration would increase peak power. This explains why femtosecond are commonly employed in multiphoton processes.

Nonlinear fluorescence can now be expressed as a function of Energy and pulse duration:

$F\cong(Pav*E)/\tau$

This expression shows that choosing the shortest pulse duration would improve fluorescence as fluorescence evolves proportionally to $1/\tau$ .

Group delay dispersion compensation

Some commercial lasers can produce pulses of <10 fs which in theory would increase fluorescence by a factor of >10 compared to a conventional 100 fs pulse duration. In reality, this theory is limited by dispersion induced by all the optics composing the microscopy system. For pulse durations of more than 70 fs, group delay dispersion (GDD) of optical elements can be precompensated by conventional dispersive elements such as prisms often incorporated in advanced laser sources. This ensures pulse quality is maintained on the sample. However, for pulses with durations of <70 ps, higher order dispersion dominates, severely degrading pulse duration. Consequently, a laser producing <10 fs pulse duration would actually produce much lower fluorescence compared to a laser producing 100 fs pulse duration. This is why femtosecond lasers employed in multiphoton excitation are typically characterized by pulse durations in the range of 80 to 150 fs where GDD precompensation can be the most effective.

More average power is better

We saw peak power as a crucial factor to define the fluorescence factor $F$ . Energy is also defined by repetition rate $R$ and average power $Pav$ :

$E=Pav/R$

Leading to the following definition of fluorescence factor $F$ :

$F\cong〖Pav〗^2/(t*R)$

This relation demonstrates that for a laser with given repetition rate and pulse duration, fluorescence increases quadratically as a function of average power. Previously, we also found out that optimal pulse duration must be larger than 70 fs to avoid higher dispersion and shorter than 150 fs to keep high peak power. With limited possibilities to optimize pulse duration, average power becomes the most significant parameter to increase nonlinear fluorescence.

Limitations of laser power scaling in in-vivo bio-imaging

While the theory shows that more power generates higher multiphoton excitation fluorescence, this can also create photobleaching or potentially damage living samples. This greatly limits the use of higher average power in in-vivo microscopy systems. If too much optical power can damage a single spot, then it offers the possibility to excite multiple sites with well-defined power levels on each site. This strategy is used today by several laboratories, pushing the need for femtosecond lasers producing higher and higher average power.

How changing repetition rate can help

Since high average power may damage biological living samples, one may increase fluorescence efficiency while keeping average power to a reasonable level, by decreasing repetition rate. This possibility is offered by new fixed wavelength lasers as well as OPCPA based lasers. Decreasing repetition rate presents various benefits in multiphoton microscopy but also in optogenetics where higher pulse energy is required to excite a wider population of neurons while operating below damage threshold of living cells.

2-Photon Microscopy: XSight’s Vision for a Simplified Experience

The ALCOR Series of femtosecond lasers can be equipped with the optional XSight, fully-integrated electronics module for 920nm & 1064nm, allowing for easy power adjustments and modulation. By itself, the ALCOR is an excellent laser for Two-Photon Imaging applications, offering fixed output powers of 1W, 2W, 4W, and 5W, but has no power modulation, and can only operate in alignment power mode, or full power mode, with no intermediate power levels. With the addition of the XSight module, users can tailor the output power to achieve the best results from their specific application. Rather than offering one configuration with all the bells and whistles, the modular design of the ALCOR Series allows you to save money on unnecessary components if your project doesn’t require the advanced features. Additionally, while there is a loss of total transmitted power when adding the XSight module, the transmission efficiency is one of the highest on the market for this type of laser, coming in at an impressive 85%.

Read the full article here.

Femtosecond Lasers for Material Processing and Micromachining Applications

The primary application for femtosecond lasers is micromachining, which can include consumer, medical or R&D applications. Typically, these applications require femtosecond pulses for their cold-ablation affects. Femtosecond lasers are ideal tools for applications where micro-cracks, HAZ, or recasts are detrimental to the integrity or lifetime of the material being processed.

A growing application for femtosecond lasers is in the field of handheld electronics…more specifically cell phones and tablets. Manufactures are experimenting with different materials to make a more robust product. The popularity of ultrafast femtosecond lasers continues to grow in these challenging industrial applications that require cold ablation.

Our femtosecond micromachining lasers can be applied to a variety of industrial processes, including cold ablation, semiconductor processing, stent cutting, laser marking, TFT repair, thin film patterning, marking, dicing, scribing, solar cell cutting, edge isolation, laser deposition, surface patterning, processing volatile materials, or machining hard materials. Femtosecond lasers are also used in various medical procedures within the ophthalmological and dermatological fields

Femtosecond lasers microstructure (groove, cut, drill, micromill, etc.) virtually any material with:

no thermal side-effects such as microcracks, burrs, or recast
lateral features as small as a few um
pulses-on-demand for easy integration into delivery systems
high average power, pulse energy and rep rate for increased ablation rate per pulse

Examples for industrial femtosecond laser micromachining can include:

IMD – medical and biomedical devices (PMMA, PLLA, catheters, stents, pacemakers, guidewires, cutting, drilling, de-coating, etc.)
FPD- flat panel display (AMOLED, OLED, Quantum Dots panels)
Micro and nano-processing of complex materials (glass, ceramics, quartz, sapphire, organic tissues, etc.)
Surface texturing

Read the full article here.

How Can We Help?

If you have any questions, or if you would like some assistance please Contact Us here. Furthermore, you can email us at info@rpmclasers.com to talk to a knowledgeable Product Manager.

Alternatively, use the filters on this page to assist in narrowing down the selection of Femtosecond lasers for sale. Finally, head to our Knowledge Center with our Lasers 101 page and Blogs, Whitepapers, and FAQ pages for further, in-depth reading.

Finally, check out our Limited Supply – In Stock – Buy Now page: This page contains an ever-changing assortment of various types of new lasers at marked-down/discount prices.

Additional Resources

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Part Number	Type	Wavelength (nm)	Output power (W)	Pulse energy (uJ)	Pulse width	Rep rate	Q-switch type
ALCOR 10XX	Pulsed DPSS Lasers, Pulsed Fiber Lasers, Ultrafast Lasers	1040, 1064	2.0, 5.0	0.025, 0.062	100fs, 110fs	80MHz (Optional: 40MHz)	Active
ALCOR 520	Pulsed DPSS Lasers, Pulsed Fiber Lasers, Ultrafast Lasers	520	0.800, 2.0	0.025	180fs	80MHz (Optional: 40MHz)	Active
ALCOR 780	Pulsed DPSS Lasers, Pulsed Fiber Lasers, Ultrafast Lasers	780	0.800	0.010	150fs	80MHz (Optional: 40MHz)	Active
ALCOR 920	Pulsed DPSS Lasers, Pulsed Fiber Lasers, Ultrafast Lasers	920	1.0, 2.0, 4.0	0.0125, 0.025, 0.050	100fs, 110fs, 130fs	80MHz (Optional: 40MHz)	Active
ALCOR Dual	Pulsed DPSS Lasers, Pulsed Fiber Lasers, Ultrafast Lasers	920/1064	1.0, 2.0	0.0125, 0.025	100fs, 110fs, 130fs	80MHz (Optional: 40MHz)	Active
Altair	Pulsed DPSS Lasers, Pulsed Fiber Lasers, Ultrafast Lasers	1040	10.0, 20.0	0.125, 0.250, 1.0	150fs, 250fs	30MHz, 80MHz, Single shot to 40MHz	Active
Diadem 1300	Pulsed DPSS Lasers, Ultrafast Lasers	1300	2.0	1.0	150fs	Single shot to 2MHz	Active
Diadem IR	Pulsed DPSS Lasers, Ultrafast Lasers	1030, 1064	10.0, 20.0, 30.0	10.0, 20.0, 30.0, 40.0	400fs, 10ps	Single shot to 2MHz	Active
neoMOS	Pulsed DPSS Lasers	1064	5.0, 15.0, 50.0, 75.0, 100.0	250.0, 400.0, 500.0	600fs, 700fs, 900fs, 10ps, 40ps, 70ps, 100ps
neoYb	DPSS Amplifiers	1030	100.0	50.0, 500.0	700fs, CW

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Alcor Series

Alcor

ALCOR is the most advanced femtosecond fiber laser emitting at 920 nm or 1064 nm specifically designed for multiphoton microscopy instrumentation and industrial OEM integration, working with 24/7 operations, in an ultra-compact, robust and air-cooled format. Featuring the Alcor 920 4W, with the highest average power commercially available, as well as the XSight and FLeXSight external modules, allowing for fine and fast gating and power control, and GDD precompensation.

Altair Series

Altair: Femtosecond Laser

The ALTAIR is an ideal solution for biophotonics applications such as multiphoton microscopy where deep excitation of red-shifted indicators such as RCaMP, dtTomato, and MCherry is required. Providing <160fs pulses, average power up to 20W and peak power up to 1.5MW at 1µm, the ALTAIR is the preferred solution for both OEM and researchers in the microscopy and lifesciences fields. The fiber-based design ensures robust and reliable 24/7 operation while providing supreme pulse quality from a user friendly, ultra compact air-cooled package.

Diadem Series

DIADEM Series

DIADEM Series is a compact, air-cooled, high energy ultrafast laser for advanced micro-machining applications that require short femtosecond pulse widths. The Diadem is available with up to 40µJ of pulse energy, 30W of average power, and operation up to 1MHz (standard), with pulses below <400 fs and an M² < 1.2. This laser has been specifically designed for demanding medical implantable device and electronics manufacturing as well as high peak power optogenetics applications.