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The Photonics Spotlight

The Photonics Spotlight – associated with the Encyclopedia of Laser Physics and Technology – is a “blog” (web log) with the purpose of highlighting interesting news and useful information in the area of photonics, particularly laser technology and applications. The content can be related to particularly interesting scientific papers or to other forms of publications, reporting for example cute new techniques, special achievements, or useful hints.

Note that the Spotlight articles (as well as those of the Encyclopedia) are citable. Permanent links are given for each article.

This blog is operated by of RP Photonics Consulting. Comments and suggestions are welcome. The news items are definitely not available for advertising, but advertisers can order banners on the right column of this page.

You can read this content in various ways:

If you like this resource, share it with your friends and colleagues, e.g. via social media:

And here are the articles:

Attenuating Laser Beams – not That Easy

Ref.: encyclopedia article on optical attenuators

In principle, attenuating a laser beam, i.e., reducing its optical power, is an easy thing: simply send it through a partially absorbing medium, or exploit a partial reflection. In practice, however, various nasty problems can arise, some of which are discussed in the following.

Thermally Induced Distortions

Because laser beams often carry substantial optical powers, absorption of a significant part of that power can lead to substantial thermal effects. Therefore, e.g. absorbing neutral density filters are often not suitable for such purposes: the increased temperature in the glass would lead to strong thermal lensing effects, which can focus the beam and distort its spatial profile.

For higher powers, the glass could even be fractured; a few watts would usually be sufficient for that effect.

Interference Effects

For attenuating the output of a single-frequency laser with a moderate optical power (a few hundred milliwatts), I once (being a beginner in the field) used several neutral density filters in series. I was then very astonished and frightened to see the transmitted power dropping strongly within a few seconds after turning on the laser; initially, I thought the laser had been damaged. It turned out that due to the significant reflectivity of these filters, I had actually realized a Fabry–Perot interferometer. When this got into resonance, a relatively high optical power was circulating between the surfaces of two filters, and that heated these filters such that their surfaces were somewhat bulged. That in turn tuned the resonance frequency and thus influenced the circulating power. Due to the resonance effect, the transmitted power was also far higher than expected.

It turned out that I had to somewhat tilt the filters against the beam such that no light could circulate between them. That was an easy measure, but I had already spoiled some spots on the filters by overheating. Only the resonance effect produced enough heat for damage of the parts.

Spatial Inhomogeneities

When monitoring the output power of the high-power laser with a photodiode, a high degree of attenuation of the power is required.

It may sound clever if you utilize not the actual output beam, but rather a parasitic beam getting through a highly reflecting mirror of the laser resonator due to the non-perfect reflectivity. Then you do not have to place additional things into the output beam and do not lose any useful output power.

However, it can be problematic that the residual transmission of a highly reflecting mirror can strongly depend on the exact position on the mirror. Therefore, if you align the laser resonator for maximum power on your photodiode, you may actually spoil the laser alignment because you actually optimize concerning the spot on the mirror having the highest transmission! (If the responsivity of your photodiode is not uniform, e.g. due to damaged spots, you can have the same effect even with perfect beam attenuation.)

Similar problems can occur when you want to measure the laser beam quality. The beam transmitted through a highly reflected mirror may have a better suited power for such a measurement, but can be severely distorted, thus exhibiting a substantially lower beam quality than the actual output beam.

For such reasons, it is better to use several mirrors in series, where each mirror does not attenuate the beam that strongly.

Polarization Effects

Another seemingly clever idea would be to reflect a linearly polarized laser beam with p polarization at a glass surface, choosing an incidence angle close to Brewster's angle. There, the reflectivity is very small, so that the reflected beam is strongly attenuated.

The caveat is that in this configuration you get a far higher reflectivity for s polarization, and even a nominally p-polarized beam will in practice have some fraction of its power in the other polarization direction. Therefore, the reflected beam may be stronger than you expect, and it may also exhibit a curious beam profile. This is because light in the nominally absent polarization direction often gets there by thermally induced depolarization effects e.g. in a laser crystal, which are not radially symmetric.

Therefore, it is again better to use reflections on subsequent surfaces, where the attenuation per reflection is not too strong.

A common method of obtaining an adjustable degree of attenuation is to use a half waveplate in combination with a polarizer. This works quite well for linearly polarized input beams, but again there are limitations due to non-perfect properties of the waveplate and the polarizer. You may not be able to reliably achieve a very high degree of attenuation, and of course you depend on a stable polarization state of the input.

Beam Offsets

In some cases, you need to attenuate a laser beam without changing its direction. Many methods of attenuation, however, deflect the beam or at least cause a parallel beam offset, the magnitude of which may vary if you change the degree of attenuation. Some kinds of variable optical attenuators have been constructed where such effects are avoided by compensation. For example, you may have a certain beam offset upon transmission through an angled plate, which is compensated by transmission through another plate oriented at the same angle. Of course, one requires high-quality fine mechanics for preserving the beam direction and position precisely.


We can only conclude that optical attenuation is not quite as easy as one might think before having tried! This is ultimately the reason why optimized optical attenuators can be sold at substantial prices. See, for example, the page on optical attenuators in the RP Photonics Buyer's Guide.

New Tutorial: Modeling of Fiber Amplifiers and Lasers

Ref.: tutorial “Modeling of Fiber Amplifiers and Lasers

Today, I have published on our website a new tutorial with the title “Modeling of Fiber Amplifiers and Lasers”. Last year, I already published tutorials on passive fiber optics and on fiber amplifiers. In contrast to these, the new tutorial mainly focuses on various aspects of developing and using laser and amplifier models. It is intended to help particularly those who would like to get into this area – either by developing the required software themselves or with commercial software.

I believe that computer modeling will become more and more important in the field of photonics. We still have many development teams and research groups not using such powerful tools, instead relying a lot on trial and error in the laboratory. This is often highly inefficient, however, and this in many ways. One spends time and money for purchasing parts which may not work in the end (e.g. due to wrong design of the setup), and perhaps more importantly spend a lot of time in the lab without making efficient progress. Spent salaries during the wasted time are often only the smaller part of the damage, as there are also infrastructure costs, and lost opportunities in terms of exploiting market potentials or publishing findings in time can even be more damaging than that.

Even if you clearly see in the lab that some setup doesn't work, it is often far from obvious why it doesn't or what you should do to make progress. You then always have to somehow interpret the situation based on some kind of theoretical model – be it a set of vague ideas in your mind or quantitative computer model with which you can really check certain ideas, explanations or possible improvements.

I regularly see people considering whether they can afford to spend a certain amount of money and time for getting into modeling of their devices. Actually, I believe that this is the wrong question. One should determine what is the most efficient way of reaching the central goals, and you cannot afford not to do it in the most efficient way!

Anyway, I hope that this tutorial will help many industry people and researchers to develop clear thoughts on many issues, including both technical and non-technical ones, and thus to make good progress in their jobs. Enjoy the reading!

How PhD Students Should Get Supported by Supervisors

We are dealing with a hot topic, even with relations to ethical guidelines and science fraud.

Today I would like to cover a topic which is not specific to photonics, but of general interest for the scientific community. I would like to emphasize at this point already that my article does not only touch the interests of students, but also hot topics like authorship and science fraud. (For some, the topic may even be too hot to share the article with their supervisor!) Hopefully, these thoughts will find some resonance, as I believe that this could result in great benefits not only for the quality of life of many researchers, but also for the quality and effectiveness of scientific research.

In my career as a researcher, I obtained insight into a number of research groups. There, I recognized substantial differences concerning the conditions under which PhD students are working. Some of them are related to the structure of the research group, e.g. whether there are staff members in intermediate positions (e.g. senior research assistants) in addition to a professor as the head of the group. In addition, there appear to be quite different ideas concerning what to expect from PhD students and from their supervisors. Maybe not all of these ideas have resulted from thorough reflections.

What Students Can Do, and What is Difficult

Certainly, PhD students play a vital role in most research groups. They often do the largest part of the laboratory work, like working out detailed plans for experiments, ordering needed equipment or even setting up whole labs, performing much of the experiments and interpreting experimental results. Many of them work quite hard and acquire a rather solid level of scientific and technical competence during these years.

Formulating a concrete plan for a suitable research project is a difficult task – normally requiring more experience than a beginning PhD student can have.

What is really difficult for beginning PhD student is to identify a suitable research project. After all, this requires a substantial knowledge on pre-existing work, a vision of what could and should be accomplished next, and to a realistic appreciation of the possible difficulties to be encountered in a certain project. Even though one rightly expects a PhD student to accomplish substantially more than only thoroughly carrying out a predefined plan, I believe it would normally be far too much to ask from a PhD student to work out the whole plan for his studies himself. Particularly in the early stages, vital inputs from an experienced supervisor are deadly needed.

A research project can get into a crisis, the management of which often requires more than can be expected from a student alone.

Even a well planned research project pursued by a good student can get into trouble e.g. if certain unexpected technical difficulties arise or if utterly unexpected findings are made which make the original plan obsolete. A student who is left alone in such a situation without substantial help – or even worse, with additional pressure coming from the boss, can easily get into despair. If this results in the failure of the project, the whole career can be at stake. It can be an invaluable benefit in such a situation to receive competent help and moral support from an experienced supervisor, for whom it is easier to judge a complex situation, to analyze the magnitude of the encountered difficulties and to identify the best way out of the crisis.

Benefits Provided by Supportive Supervisors

I would like to emphasize that a supervisor who sees his task in supporting students will not only avoid serious trouble and a very uncomfortable time for the student, but also contribute greatly to the success of the research group as a whole. He or she will bring important contributions to the productivity of the students' work and will also contribute to the team spirit which makes the research more pleasant for everybody and more productive due to fruitful cooperation, which can arise only on the basis of mutual trust. In the end, everybody will profit from that.

There are group leaders, however, who are too strongly focused on their personal career and seem to feel that they have no resources left for supporting others. Some of these leave students alone in trouble, while others even increase the trouble by mounting additional pressure – sometimes with the doubtful idea that this may lead to harder work by the student which will eventually solve the problem.

The Relation to Authorship Practices

An important question is who really deserves authorship in scientific publications. There is normally no question whether the student, having done most of the work, obtains a prominent position in the list of authors, but whether supervisors are to be listed there as well is a more delicate question. Generally, nobody should be an author who has not brought concrete important contributions to the published work. Amongst those who seriously dealt with this question, there seems to be a widespread consensus that it is absolutely not sufficient for authorship

  • to be the leader of a group,
  • to have produced the original idea for the project without having worked out any details, or
  • to have read the final publication and made a few minor corrections to it.

Breaching theoretically valid authorship guidelines is still quite common, unfortunately. Some are lacking the power to fight, while others have different priorities.

Unfortunately, many supervisors (senior research assistants and particularly professors) still believe that they are automatically entitled for authorship on anything being done in their group. They consider it sufficient to have produced some vague ideas or to have paid (of course not with their own money!) for the used infrastructure, for example. Of course, a PhD student is normally not in the position to argue about such points, given the enormous discrepancy of power between him or her and the professor. Unfortunately, at many places there appears to be nobody who would be able and willing to enforce the authorship practices which are theoretically demanded from everyone. I have even experienced a case where most obvious abuse by a professor (demanding the authorship on a whole book chapter without having written a single sentence of it) has been explicitly defended rather than prosecuted by the highest ranks in a highly esteemed research institute. Obviously, these people were being less interested in upholding ethical standards than in avoiding trouble with that professor.

If serious engagement were the condition of authorship of supervisors, supervisors would be more likely to do their job.

You may ask what that problem has to do with supporting students, the topic of my article. Imagine that justifiable authorship practices would be enforced throughout in universities. As a result, professors (particularly those having large groups) could no more claim authorship in many cases where they did before. This would create an incentive not to set up huge groups without having any time to support the students, but rather to form smaller groups and to actively participate in the research. I believe that this would in the long term lead to a stronger cooperation between the different ranks in a group and that way to more productive and efficient research.

I know that not every senior researcher is able to really bring such valuable contributions as outlined above; in some cases, the students may actually be more happy to be left alone. However, if that were a serious counterargument, one might as well stop employing students on the basis that some of them turn out not to be sufficiently competent.

Supporting Students and Preventing Science Fraud

There is also a relation between the support for students and the prevention of science fraud – but not what many might think! I sometimes read that students would be prevented from forging results if they were under closer control, but I believe that this view is distorted:

A substantial risk for science fraud arises only in a serious crisis – and is in that case strongly dependent on how the supervisor performs!

The risk for fraud is surely far higher than under normal conditions if a student's project gets into a crisis (as described above) and there is no support available. Even worse, the supervisor may mount additional pressure and in that way make the student feel that the only way out very serious trouble is to produce results somehow – be it with fraud or at least doubtful practices if no other way can be seen. On the other hand, imagine a helpful supervisor, where a student has a very attractive option: just to go there, openly discuss the problems and obtain valuable help for solving the problems. Which student would be crazy enough to forge results rather than to accept valuable help?

After certain scandals became public, I asked myself whether I could rule out the possibility that a student could once have forged results without me noticing it. The answer: I am sure there would have been ways to accomplish that, but I also firmly believe that it never happened – simply because there was never an incentive for a student to do so. While I never treated my students as schoolboys who need to be observed in every moment, I was always prepared to work hard in order to bring really helpful contributions when a project encountered difficulties.

When thinking seriously about these things, I believe one can only come to the conclusion that a large part of the responsibility for providing science fraud is on the side of supervisors. As long as these do their job well, I believe there is a minimal risk of fraud. On the other hand such a risk can become substantial if people are sliding into a situation where fraud appears to be the only way to avoid dire consequences. Just telling students that fraud is evil will certainly not solve the problem – I am sure they all know that.

You may also like to read an article which I wrote five years ago: "Risk factors for scientific fraud and the scientist's responsibility".

Older Postings

2014-11-14: Correctly Designing Frequency Conversion Stages: Not Easy, but Worthwhile!

2014-10-03: Fiber Optics Tutorials

2014-07-28: How to Define the Mode Radius of a Fiber?

2014-06-27: Shortages of Rare Earth Materials – a Problem for Photonics?

2014-05-16: 10-Year Anniversary of RP Photonics

2014-04-02: Lower Emission Cross-section Leads to Higher Pulse Energy?!?

2014-01-17: Mediation in Disputes on Laser Technology

2013-12-13: Avoiding Trouble with Laser Specifications

2013-11-12: Beam Quality Limit for Multimode Fibers

2013-09-24: Simulation of a Q-switched Nd:YAG Laser:
Numerical Beam Propagation Reveals What Happens, Analytical Reasoning Explains It

2013-08-26: Frequency Doubling and the Reverse Process

2013-07-08: Amplified Spontaneous Emission in Fiber Amplifiers

2013-06-13: Two New Photonics Newsletters

2012-08-06: The New RP Photonics Buyer's Guide

2012-03-12: New Raman Lasers

2012-03-03: Conflicting Definitions of s and p Polarization

2012-02-03: Simulation Software: Use Commercial Products or Home-Made Software?

2011-12-23: Kerr-lens Mode-locked Thin-disk Laser

2011-06-10: Are Compact Resonators More Stable?

2011-05-28: Explanation for the Mode Instability in High-power Fiber Amplifiers with Few-mode Fibers

2011-03-13: What if Solid-State Laser Transitions Would Be Much Stronger?

2011-02-10: Fiber Lasers: More Difficult to Design than Bulk Lasers

2011-01-05: Femtosecond Fiber Amplifiers: Unlimited Peak Power?

2010-09-02: Why LEDs are Energy-efficient, and Why They Could Well Increase Energy Consumption

2010-07-27: Special SESAMs for Mode-locked High-power Lasers?

2010-07-12: Laser Development: Get an Expert Early on!

2010-06-09: Poor Man's Isolator

2010-05-14: Plagiarism, Exploiting the Encyclopedia of Laser Physics and Technology

2010-04-26: Resolution and Accuracy of Measurements

2010-04-16: Why Large Mode Area Waveguides Do Not Work for Laser Diodes

2010-04-08: Creating a Top-hat Laser Beam Focus

2010-03-22: All-in-one Concepts versus Modular Concepts

2010-03-15: Spatial Walk-off and Beam Quality in Nonlinear Frequency Conversion

2010-03-09: Nonlinearities in Fiber Amplifier Modeling

2010-03-03: Thresholds for Nonlinear Effects in Fiber Amplifiers

2010-02-26: New Scientific Paper: Timing Jitter and Phase Noise of Mode-locked Fiber Lasers

2010-02-06: Scientific Conferences and Publications: Emphasize Device Performance or Insight?

2010-01-29: Far From Maturity: The Photonics Industry

2010-01-22: Pumping Fiber Lasers with Fiber Lasers

2010-01-11: Beams of Laser Pointers: Visible in Air?

2009-12-31: Tilt Tuning of Etalons

2009-12-13: Johnson–Nyquist Noise in Photodiode Circuits

2009-12-08: Increased Output Power of a Laser with Forced Tuning

2009-11-22: The Beam Focus – Not Just a Demagnified Version of Your Beam

2009-11-18: Articles and a Quiz on Photonics Issues

2009-11-13: Photodetection: Optical and Electrical Powers

2009-11-03: Coherent Light from a Bulb?

2009-10-19: Risk Factors for Science Fraud and the Scientist's Responsibility

2009-10-12: Cold Light from the Hottest Bodies and from Cool Devices

2009-10-08: Nobel Prize for Charles K. Kao for Pioneering Work on Optical Fibers

2009-10-03: Peak Intensity of Gaussian Beam

2009-09-27: Lasers with Short Upper-state Lifetime

2009-09-19: Are Laser Resonators Power Scalable?

2009-09-07: Anniversary: 5 Years of the Encyclopedia of Laser Physics and Technology

2009-09-01: Fresnel Reflections from Double Interfaces

2009-08-22: Jitter and Phase Noise of Mode-locked Fiber Lasers

2009-08-14: Progress on Green Laser Diodes

2009-08-12: What is an Optical Transistor?

2009-07-29: No Beat Note for Orthogonal Modes

2009-07-23: Submit Photographs for the Encyclopedia of Laser Physics and Technology

2009-07-21: Signal-to-Noise Ratio and Measurement Bandwidth

2009-07-09: Gain-guiding Index-antiguiding Fibers

2009-06-29: Doing Things Properly: It's the Economy, Stupid!

2009-06-23: Coherence – a Black-or-White Issue?

2009-06-08: Prizes of the European Physical Society

2009-06-02: 5 Years of RP Photonics Consulting

2009-05-22: Interference Effects with Imbalanced Intensity Levels

2009-05-13: The Minimum Time–Bandwidth Product

2009-04-28: SPIE Field Guides

2009-04-19: Last Chance to Get the Encyclopedia of Laser Physics and Technology Cheaper

2009-04-17: Miniature Laser Projectors – The Next Big Laser Thing?

2009-04-06: Laser Pointers in Soccer Games: Not Necessarily Harmless

2009-04-05: Stability of Resonators – an Ambiguous Term

2009-03-19: Scientific Progress: not as Straight a Process as it Seems

2009-03-07: Complicated Pulse Shapes from Q-switched Fiber Lasers

2009-03-02: User Interfaces for Simulation Software

2009-02-13: Laser Beam Deflections: The Angle–Diameter Product

2009-01-12: Chaotic Lasing Generates Random Numbers

2009-01-05: Extremely Long Mode-locked Fiber Laser

2008-12-16: Why Fiber Amplifiers, not Fiber Lasers?

2008-11-25: The Gouy Phase Shift Speeds up Light

2008-11-08: Validating Numerical Simulation Software

2008-10-20: Rate Equations – An Example for Stiff Sets of Differential Equations

2008-10-03: Wavelength-Tunable Lasers: Does the Tuner Degrade the Power Efficiency?

2008-09-24: Decoupling Pulse Duration and Pulse Energy

2008-09-10: Unpolarized Single-Frequency Output

2008-08-28: Photographs for the Encyclopedia of Laser Physics and Technology

2008-08-15: Print Version of the Encyclopedia of Laser Physics and Technology

2008-07-26: Beat Signals with Zero Linewidth

2008-07-13: The Simplified History of the Michelson–Morley Experiment

2008-07-02: Stronger Focusing Avoids SESAM Damage

2008-06-20: All-in-One Ultrafast Laser Systems

2008-06-13: Heisenberg's Uncertainty Principle and the Transform Limit

2008-06-06: Fiber Lasers Which Are No Fiber Lasers

2008-05-25: Einstein and the Laser

2008-05-13: Easier Self-Starting Passive Mode Locking for Short Lasers

2008-05-05: Length of a Photon

2008-04-28: Different Kinds of Polarization

2008-04-22: Abused Photonics Terms: Coherence

2008-04-15: Abused Photonics Terms: Modes

2008-04-02: Solitons: Lower Dispersion, Stronger Dispersive Effects!

2008-03-26: Mode-Locked Lasers: Lower Average Powers in Shorter Pulses

2008-03-17: Ultrafast Fiber Lasers: Re-Inventing Mode Locking

2008-03-10: Automatic Phase Matching

2008-03-04: What is a “High” Laser Beam Quality?

2008-02-22: Launching Light from a Bulb into a Single-Mode Fiber

2008-02-14: How Laser Development Can Go Wrong

2008-02-12: Factor 2 in the Equation for Cross-Phase Modulation

2008-02-03: Quantifying the Chirp of Ultrashort Pulses

2008-01-27: Beam Quality in Second-Harmonic Generation

2008-01-14: Frequency Doubling: Long Pulses Cause Trouble

2008-01-06: Saturation Intensity or Saturation Fluence of a Saturable Absorber or a Laser Gain Medium: What Matters?

2007-12-18: The Role of Laser Safety Goggles

2007-12-11: The Idler Wave - Essential for Parametric Amplification and Oscillation

2007-12-03: New Paper on Power Scaling of Lasers

2007-11-26: Solving Laser Problems Step by Step

2007-11-19: Walk-Off and Phase-Matching Bandwidth in Nonlinear Crystals

2007-11-10: Retirement of Prof. David C. Hanna

2007-11-02: Ultrafast Laser Kills Viruses

2007-10-31: Thermal Equilibrium in Laser Crystals

2007-10-25: The Gain Bandwidth of Laser Crystals and Glasses

2007-10-17: Why the Second-Harmonic Beam is Smaller

2007-10-11: Understanding Fourier Spectra

2007-10-07: Effective Refractive Index: Correcting a Common Belief

2007-09-27: Light Plus Light = Darkness: No Energy Problem, but Quantum Weirdness

2007-09-21: Optimum Crystal Length for Frequency Doubling

2007-09-13: Using Figures of the Encyclopedia in Your Publications, and Citing the Encyclopedia

2007-09-07: Power Scaling in Downward Direction

2007-09-01: Stimulated Brillouin Scattering: Lower Peak Power, Stronger Effect?

2007-08-27: Distant Healing of Lasers

2007-08-23: An OPO Without Resonator Mirrors

2007-08-22: Saturation of Pump Absorption - An Important Issue?

2007-08-15: Light = Electromagnetic Waves?

2007-08-06: Fiber Amplifiers: More ASE for Larger Core with Higher NA?

2007-07-30: Fiber Amplifiers: Stronger ASE in Backward Direction

2007-07-25: Higher Heat Generation Density, Stronger Thermal Effects?

2007-07-16: Mode Competition - Increased or Decreased by Spatial Hole Burning?

2007-07-11: What is a Beam Width, Beam Size, and a Beam Waist?

2007-07-06: Promoting Dangerous Practices in Laser Labs

2007-07-01: Nonsensical Regulations Undermine Laser Safety

2007-06-24: The Plague of a Narrow Emission Linewidth

2007-06-11: Beam Quality Measurements Can Easily Go Wrong

2007-06-01: Characterize Your Pump Beam!

2007-05-26: Optical Isotropy: Nonlinear Interactions are Different!

2007-05-19: Why Strong Birefringence in Fibers Helps

2007-05-10: Fundamental Limitation for sigma-tau Product, Gain Efficiency, and Laser Threshold

2007-04-28: Easier Launching into Fibers with Large Mode Area?

2007-04-16: Questions and Answers on Shot Noise

2007-04-01: The Ideal Pump Intensity Distribution in an End-Pumped Solid-State Laser

2007-03-23: Explaining the Nature of Photons to Lay Persons

2007-03-16: Time To Market and the Economics of Laser Development - or How to Cause Great Financial Damage without Spending Money

2007-03-11: Divided-Pulse Amplification

2007-03-09: The Trouble with Crystal and Coating Damage

2007-03-05: More Efficient Frequency Doubling with Shorter Pulses?

2007-02-26: No Laser, no Result?

2007-02-22: Lossy Laser Cavities

2007-02-16: The Science of Biophotons

2007-02-09: Papers Reporting Yet Another Laser Crystal

2007-02-04: Continuing Struggle for Larger Fiber Mode Areas

2007-01-27: Noise Figure of Amplifiers

2007-01-21: Operation Far Above Threshold

2007-01-15: Origins of Heating in Laser Crystals

2007-01-09: The Myth of Fiber-Optic Polar Bears

2007-01-05: Why the Encyclopedia of Laser Physics and Technology is Successful

2006-12-31: Peak Position of an Optical Spectrum

2006-12-16: Dangerous Green Laser Pointers

2006-12-09: The Laser Industry - High Tech or Low Tech?

2006-12-03: Diffraction in Optical Fibers

2006-11-28: The Role of Diffraction in Optical Resonators

2006-11-21: The Resonator Mystery

2006-11-16: Laser Models - not Always Useful

2006-11-04: Nd:YVO4 Laser with Polarization-Independent Pump Absorption

2006-11-02: Reflection Spectrum of Tilted Dielectric Mirrors

2006-10-26: Residual Transmission Through Highly Reflecting Mirrors

2006-10-22: Lasers Attract Dust to Cavity Mirrors

2006-10-17: A Cute New Imaging Technique Named Compressive Imaging

2006-10-16: Using a Current Amplifier for Optical Power Measurements and Recording with a Photodiode

2006-10-15: Fivehundred Articles in the Encyclopedia of Laser Physics and Technology

2006-10-09: Correct Specifications for Laser Noise - Valuable but Hard to Obtain

2006-10-04: Higher-Order Modes of Fibers: a Solution for Single-Mode Guidance with Large Mode Area?

2006-10-01: Stability Zones of Laser Resonators

2006-09-29: Frequency Dependence of the Conversion Efficiency for Frequency Doubling

2006-09-22: Coherence Length of Ultrashort Pulses

2006-09-21: Power Scaling Limits of Optical Parametric Amplifiers

2006-09-16: Q-switched Lasers: YAG versus Vanadate

2006-09-06: Quenching Degrades the Efficiency of Some Ytterbium-Doped Gain Media

2006-09-03: Single-Frequency Operation Stabilized by Spatial Hole Burning

2006-09-03: Resolution of Conundrum: Threshold Power for Parametric Nonlinear Interactions

2006-09-01: Test Yourself with the Photonics Quiz

2006-08-23: Lasers with Nonlinear Input-Output Characteristics

2006-08-20: Lower Noise from Longer Lasers

2006-08-18: Resolution of Conundrum: No Magnetic Field on the Axis of a Coil

2006-08-15: The Effect of a Double Pass in a Frequency Doubler

2006-08-12: Understanding Quasi-Three-Level Lasers

2006-08-10: Single-Mode Fibers with Large Mode Areas

2006-08-01: Lasers Disturbed by Vacuum?

2006-07-30: Threshold Power for Parametric Nonlinear Interactions

2006-07-24: Beam Distortions in Laser Cavities

2006-07-23: Single-Atom Lasers

2006-07-22: No Magnetic Field on the Axis of a Coil?

2006-07-21: Photonics and Laser Technology Blogs – Where Are They?

2006-07-16: Spontaneous Emission and Amplifier Noise

2006-07-14: Lasers Like it Cool

2006-07-10: Strength of Thermal Lensing Effects

2006-07-05: Laser Design: Side Product or the Basis of Laser Development?

2006-07-01: Lifting the Confusion Concerning Doping Concentrations

2006-07-01: Characterizing a Cavity with a Frequency Comb

2006-07-01: With Wavelength Combs to Picometer Resolution


… and keep in mind that the competent technical consulting services of RP Photonics could be very useful for your business!

© RP Photonics Consulting GmbH contact and legal info

Free Tutorial: Modeling of Fiber Amplifiers and Lasers

We have published a new tutorial which discusses the modeling of fiber amplifiers and lasers. It addresses many questions:

Read the tutorial!

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