Can various diode lasers of equal power be mixed to produce sum/differce freq laser?

[frank_1257]

Oh jeez, I joined a free students physics forum

[dar303]

haha, very entertaining thread, to see you get deeper and deeper down into this obsession!
Keep going!

[buffo]

I am curious if I could take lets say an 500mw 382nm laser diode and a lets say 910nm diode of the same power output density for a astigmatically corrected collimated beam/spot size and mix the 2 lasers and produce the difference frequency of 528nm or some other similar combination of various high power laser diodes at 382nm-920nm, I am used to doing this in audio work microwave uhf vhf. Can this be done by mixing of two lasers to produce the sum or difference frequencies???

The short answer is yes, intra-cavity sum frequency mixing can be used to create output wavelengths between the two. As for your specific example of 910 nm and 382 nm to produce 528 nm, I don't know. The physics is beyond me. If I had to guess, I would say it won't work, because the two lines to be summed are normally fairly close together. (A couple hundred nm or so) Your example has over 500 nm difference, which would seem to be well outside the norm. (Greg Makov at LSDI in Orlando might be someone who could at least point you in the right direction though.)

Sum frequency mixing (or sum frequency generation) is the principle behind most modern yellow laser pointers. That is, the pointer isn't producing red and green lines which our eyes combine to perceive as yellow, but rather it's combining two totally different IR wavelengths that are combined and then doubled to make a pure yellow line based on the difference between them. The physics is complicated (as you've no doubt already discovered).

Also, a question: Why bother making 528 nm when 532 is so close to it (and a whole lot easier to make)?

Adam

[James Lehman]

There are a couple of things to think about when pondering this question.

First of all, we hear sound over about 10 octaves. We only see light in less than one octave. Sums and differences of sound waves can still be well within our hearing.

Another thing I think I was trying to get to in my first post is that when sound moves through a medium it displaces the structure of the medium in the form of a transverse wave. So, two sine waves at different frequencies will move the SAME structure. I think this might be where the sum and the difference tones come from.

With light, although photons do bump into each other, they are completely separate entities that can travel through a vacuum.

James.

[frank_1257]

I CAN SEE MYSELF READING AND REREADING THESE PARTICULAR NLO PROCESSES OVER AND OVER AGAIN AS CURRENTLY I AM NOT GRASPING THEM.

ANYONE HAVING FURTHER REFERENCES DESRCIBING THE ?OPO OPTICAL PARAMETRIC OSCILLATION PROCESS, WELL THESE ARE GREATLY APPRECIATED!

[frank_1257]

Frequency-mixing processes
One of the most commonly-used frequency-mixing processes is frequency doubling or second-harmonic generation. With this technique, the 1064-nm output from Nd:YAG lasers or the 800-nm output from Ti:sapphire lasers can be converted to visible light, with wavelengths of 532 nm (green) or 400 nm (violet), respectively.
Practically, frequency-doubling is carried out by placing a special crystal in a laser beam under a well-chosen angle. Commonly-used crystals are BBO (β-barium borate), KDP (potassium dihydrogen phosphate), KTP (potassium titanyl phosphate), and lithium niobate. These crystals have the necessary properties of being strongly birefringent (necessary to obtain phase matching, see below), having a specific crystal symmetry and of course being transparent for and resistant against the high-intensity laser light. However, organic polymeric materials are set to take over from crystals as they are cheaper to make, have lower drive voltages and superior performance.

(Whoa trigger!, so Amino Acids? are going to replace our well known and loved NLO crystals of KTP-potassium titaynl phoshate, LBO-Lithium Tri-brate, BBO, BiBO, KDP, etc etc?)

Organic nonlinear optical materials

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Organic materials are expected to have relatively strong nonlinear optical properties due to delocalized electrons at π − π* orbitals. This expectation explains extensive search for better NLO materials among organic crystals.

[edit] L-arginine maleate dihydrate (LAMD)

L-Arginine is one of the essential amino acids widely distributed in biological substances. It forms a number of salts with organic and inorganic acids showing non-linear optical properties. L-Arginine maleate dihydrate (LAMD, C6H14N4O2,C4H4O4,2H2O) is one of these L-arginine salts which is a complex of strongly basic amino acid, carboxylic acid and provides useful information in relation to molecular interaction in present day biological systems and to prebiotic self-organisms.[1] It is also a nonlinear optical material with second harmonic generation efficiency 1.68 times that of KDP.[2] LAMD crystals are grown from solution by solvent evaporation; they belong to the triclinic space group P1.

[edit] L-methionine L-methioninium hydrogen maleate (LMMM)

LMMM too belongs to the amino acid family. Crystals are grown by slow evaporation of an aqueous solution containing L-methionine and maleic acid resulting in centimeter-large crystals of a non-centrosymmetric space group.[3] They were applied for second harmonic generation of an Nd:YAG laser (wavelength 1064 nm), and SHG efficiency equal to that of KDP has been obtained.

[edit] References

1. <LI id=cite_note-0>^ S.L. Miller, E.L. Orgel, "The Origins of Life on the Earth", Prentice- Hall, New Jersey, 1974. <LI id=cite_note-1>^ "Synthesis, crystal structure and solubility of C6H14N4O2,C4H4O4,2H2O" Sci. Technol. Adv. Mater. 6 (2005) 508 (free download)
2. ^ "Crystal growth and structure of L-methionine L-methioninium hydrogen maleate—a new NLO material" Sci. Technol. Adv. Mater. 9 (2008) 025012 (free download)

Retrieved from "http://en.wikipedia.org/wiki/Organic_nonlinear_optical_materials"



[edit] Theory

A number of nonlinear optical phenomena can be described as frequency-mixing processes. If the induced dipole moments of the material respond instantaneously to an applied electric field, the dielectric polarization (dipole moment per unit volume) P(t) at time t in a medium can be written as a power series in the electrical field:
. Here, the coefficients χ(n) are the n-th order susceptibilities of the medium. For any three-wave mixing process, the second-order term is crucial; it is only nonzero in media that have no inversion symmetry. If we write
, where c.c. denotes the complex conjugate (E1 and E2 being the incident beams of interest), the second-order term in the above expansion will read
, where the summation is over
. The six combinations (nx,mx) correspond, respectively, to the second harmonic of E1, the second harmonic of E2, the optically rectified signals of E1 and E2, the difference frequency, and the sum frequency. A medium that is thus pumped by the fields E1 and E2 will radiate a field E3 with an angular frequency ω3 = m1ω1 + m2ω2.
Note: in this description, χ(2) is a scalar. In reality, χ(2) is a tensor whose components depend on the combination of frequencies.
Parametric generation and amplification is a variation of difference frequency generation, where the lower-frequency one of the two generating fields is much weaker (parametric amplification) or completely absent (parametric generation). In the latter case, the fundamental quantum-mechanical uncertainty in the electric field initiates the process.

[edit] Phase matching

The above ignores the position dependence of the electrical fields. In a typical situation, the electrical fields are traveling waves described by
, at position , with the wave vector , where c is the velocity of light and n(ωj) the index of refraction of the medium at angular frequency ωj. Thus, the second-order polarization angular frequency ω3 is
. At each position , the oscillating second-order polarization radiates at angular frequency ω3 and a corresponding wave vector . Constructive interference, and therefore a high intensity ω3 field, will occur only if
. The above equation is known as the phase matching condition. Typically, three-wave mixing is done in a birefringent crystalline material (I.e., the refractive index depends on the polarization and direction of the light that passes through.), where the polarizations of the fields and the orientation of the crystal are chosen such that the phase-matching condition is fulfilled. This phase matching technique is called angle tuning. Typically a crystal has three axes, one of which has a different refractive index than the other ones. This axis is called the extraordinary (e) axis, while the other two are ordinary axes (o). There are several schemes of choosing the polarizations. If the signal and idler have the same polarization, it is called "Type-I phase-matching", and if their polarizations are perpendicular, it is called "Type-II phase-matching". However, other conventions exist that specify further which frequency has what polarization relative to the crystal axis. These types are listed below, with the convention that the signal wavelength is shorter than the idler wavelength.
Phase-matching types()PolarizationsSchemePumpSignalIdlereooType IeoeType II (or IIA)eeoType III (or IIB)eeeType IVoooType VooeType VI (or IIB or IIIA)oeoType VII (or IIA or IIIB)oeeType VIII (or I)
Most common nonlinear crystals are negative unaxial, which means that the e axis has a smaller refractive index than the o axes. In those crystals, type I and II phasematching are usually the most suitable schemes. In positive uniaxial crystals, types VII and VIII are more suitable. Types II and III are essentially equivalent, except that the names of signal and idler are swapped when the signal has a longer wavelength than the idler. For this reason, they are sometimes called IIA and IIB. The type numbers V–VIII are less common than I and II and variants.
One undesirable effect of angle tuning is that the optical frequencies involved do not propagate collinearly with each other. This is due to the fact that the extraordinary wave propagating through a birefringent crystal possesses a Poynting vector that is not parallel with the propagation vector. This would lead to beam walkoff which limits the nonlinear optical conversion efficiency. Two other methods of phase matching avoids beam walkoff by forcing all frequencies to propagate at a 90 degree angle with respect to the optical axis of the crystal. These methods are called temperature tuning and quasi-phase-matching.
Temperature tuning is where the pump (laser) frequency polarization is orthogonal to the signal and idler frequency polarization. The birefringence in some crystals, in particular Lithium Niobate is highly temperature dependent. The crystal is controlled at a certain temperature to achieve phase matching conditions.
The other method quasi-phase matching. In this method the frequencies involved are not constantly locked in phase with each other, instead the crystal axis is flipped at a regular interval Λ, typically 15 micrometres in length. Hence, these crystals are called periodically-poled.

(Ok I bought some of this recently but have not gotten my 1319nm cavity completed for producion of 659nm from a 1319nm laser using this periodically poled , Red coated PPKTP?)

This results in the polarization response of the crystal to be shifted back in phase with the pump beam by reversing the nonlinear susceptibility. This allows net positive energy flow from the pump into the signal and idler frequencies. In this case, the crystal itself provides the additional wavevector k=2π/λ (and hence momentum) to satisfy the phase matching condition. Quasi-phase matching can be expanded to chirped gratings to get more bandwidth and to shape an SHG pulse like it is done in a dazzler. SHG of a pump and Self-phase modulation (emulated by second order processes) of the signal and an optical parametric amplifier can be integrated monolithically.

[mixedgas]

Ok, you go over to google and search SNLO, it comes from 2 download sites. Its free , but you need to explain in one short sentence why you want it. Ie "I'm a laser hobbyist and I want to experiment with 3 wave mixing". You then get to download the software. Keep in mind this is maintained by Sandia national labs. Uncle wants to know what your using it for.

Download SNLO and install it. Don't gripe to Sandia if it doesn't work. They will ignore you or come and take you away. They are kinda busy saving the world from Terrorist nukes there and you are but a fly on their ass.

Select the Qmix task bar.

Input the two wavelengths you want to mix.
Input the type of mixing crystal from the pull down list.
Input a crystal oven temp.

Out comes Phi and Theta, the two angles you need to have your crystal cut to. Note your crystal will still be a cube or rectangle, those are the angles of the crystal c axis to your optical surfaces. It doesnt work if the crystal doesnt have different refractive indexes on different optical axises, ie its a non-symetrical crystal structure.
Do bother to check if the crystal adsorbs at those wavelengths. Do bother to have it coated properly.

SNLO will also work backwards, so if you buy a crystal with phi and theta on the box, you can reverse engineer it with some practice.

OPOs are tunable versions of nonlinear mixing.

Btw, whoever posted that wiki stole a lot of it from Amon Yariv's book, did they give him any credit?

I don't know if I should encoruage you with your obsession any further.


Other parts of SNLO do other things, like calculate the power you will need and the cavity design. If you input the same wavelength twice, it does doubling as well.

BTW, it is s good manners to quote the source you paste from and not to paste the whole thing, instead provide a link so spec doesnt end up paying for excess bandwidth.

Then you realize that why you dont see multiwave nonlinear optical mixing in nature is that it only comes at power densities that don't occur in nature on earth. You need a laser to do it.

Mr Mixedgas Manors.

[mixedgas]

Your Avatar is most likely a 1064 nm yag laser from a telecom optical fiber amplifier. It was used to pump the amplifier fiber. I've seen those before. I used to have one on my bench.
I never ran it, but turn on the te cooler before you do as the SP pump diode is a older one that is quite temperature sensitive. Hint, it was made to be used by a company who's stock trades under the symbol "T"
Steve,