Diode question

Printable View

03-17-2009, 16:07
MechEng3

Diode question

If electromagnetic radiation is a self-propagating transverse oscillating wave of electric and magnetic fields.... is a said laser diode having a TE polarized emission is then subjected to a polarized filter...between the diode and SHG material..at the worst possible , being 90 deg off axis to desired....would it possibly be limiting the correct amount of TE fundamental power to be impaled upon a surface? Therefore limiting the total wavelength on the diode emission to be consumed as electric and magnetic fields as equal amounts in the SHG process? Or is there a wavelength dependant on , lets say a Yag crystal, to the amount of either or a component of either fields being present? Or would the quantum aspects of SHG be the resultant of the polarized output of the diode? If there exists a superposition of stationary charged photons.....would this not create emission?
03-17-2009, 16:18
trwalters001

Ya know... I was just wondering that the other day... :D:D:D
03-17-2009, 16:34
soforene

He lost me at "If" ................... :eek:
03-17-2009, 16:34
mixedgas

YES

mixedgas
03-17-2009, 16:39
keeperx

makes sense..

a field coupled to a state, coupled to the ground state.
03-17-2009, 19:51
allthatwhichis

Quote:

Originally Posted by soforene

He lost me at "If" ................... :eek:

At least I got as far as someone else... :o Wait, which "if"? :confused:
03-17-2009, 23:16
soforene

That'd be the first one. :D
03-18-2009, 01:15
heroic

Quote:

Originally Posted by keeperx

makes sense..

a field coupled to a state, coupled to the ground state.

It'd be like melting a sheet of Polaroid.
03-18-2009, 05:47
keeperx

Quote:

It'd be like melting a sheet of Polaroid.

it'd be more like lasing a stick of dynamite

and i understood the following

Quote:

If electromagnetic radiation is a wave of electric and magnetic fields.... being 90 deg off axis ...would this not create emission?

so my answer would be.. only slightly, only slightly.
03-18-2009, 06:24
mixedgas

depends on the receiving crystal, and intracavity polarizers, or more likely wave plates, are usually quartz.

Steve
03-18-2009, 13:15
MechEng3

OK then so if the waveplate is blocking say 80% of the TM radiation ....should it lase or not. I have a case issue with either one of these perameters are at questionable levels....without the proper means to examine. In other words will the vanadate lase at 1064nm with just one of the transverse radiation waves? Or will it not be optimal unless a balance of the two overlapping ,intertwining beams are present in the initial lasing medium? If so please state a working balnce.. .78% dopant level....sapphire bonded.
03-18-2009, 14:00
heroic

Quote:

Originally Posted by MechEng3

OK then so if the waveplate is blocking say 80% of the TM radiation ....should it lase or not. I have a case issue with either one of these perameters are at questionable levels....without the proper means to examine. In other words will the vanadate lase at 1064nm with just one of the transverse radiation waves? Or will it not be optimal unless a balance of the two overlapping ,intertwining beams are present in the initial lasing medium? If so please state a working balnce.. .78% dopant level....sapphire bonded.

There's no such thing as "just one of the transverse beams". A photon consists of both parts. It cannot exist without both.
03-18-2009, 14:04
MechEng3

Exactly...but what if one of the of the linear fields were restricted? Or a polorised diode emmission through a waveplate stopping most....but not all of one of the subjects? Lower output at a given input power level? Or no out put at all. I guess what the reality is are they equally dependant as to the amplitude of each to create a lasing state in SHG mediums? Or can there be a balance more optimal for the maximum Po?
03-18-2009, 14:04
drlava

When you block electromagnetic radiation with a polarizer I don't beleive the 'other' (E or M) component continues, they are interdependent.

If instead you are talking about limiting the pump power that reaches the crystal to only its preferred polarisation, and how much 'alternate' polarization would be beneficial, with the goal of limiting crystal overheating via 'inefficient' pump power good question. Note that polarizers can change the polarization of incoming light to their mode on a probabalistic basis with 0 probability at 90 degrees and increasing probability as the incoming polarization approaches the filter polarization. It would be an interesting experiment to see if this improves lasing efficiency when using a randomly polarized (fiber?) pump source.
03-18-2009, 14:06
heroic

Quote:

Originally Posted by drlava

When you block electromagnetic radiation with a polarizer I don't beleive the 'other' (E or M) component continues, they are interdependent.

They are, in fact, the self-same energy, converting from one form to the other every half-cycle. If you block one, the other is blocked too.

Your question is like asking, if I'm talking on the phone, sound energy is converted to electrical energy, and then back to sound energy. Well what happens if I cut the phone line? Can the person on the other end still hear me?
03-18-2009, 14:07
drlava

right, they are interdependent. But that's not what he's asking.
03-18-2009, 14:08
MechEng3

Not to let a cat out of the bag...but I have a laser here that has a similar setup and questions arrise....there is a near zero measured loss of pump power as it is....I will remove the plate later tonight and rotate it to examine if a change takes place. 7.3 watts out of the diode....7.193 watts through the first set of pump shaping optics.
03-18-2009, 15:14
mixedgas

Quote:

Originally Posted by MechEng3

OK then so if the waveplate is blocking say 80% of the TM radiation ....should it lase or not. I have a case issue with either one of these perameters are at questionable levels....without the proper means to examine. In other words will the vanadate lase at 1064nm with just one of the transverse radiation waves? Or will it not be optimal unless a balance of the two overlapping ,intertwining beams are present in the initial lasing medium? If so please state a working balnce.. .78% dopant level....sapphire bonded.

Undoped vandate is used for its remarkable polarization properties. Ie its cheaper then calcite and coveres the near and mid IR. So yes, it could/would be pol sensitive.

waveplates dont block, unless something is badly wrong, ie the waveplate has developed F centers and solarized, in the IR, that would be rare. waveplates, you rotate until the fields match. Sometimes waveplates have a crystal structure that shears off in layers like mica. Did you find junk in the housing?

. Polarizers however, can and will block.

Steve
03-18-2009, 16:32
MechEng3

I feel as if the designer has placed this unit in place to keep any back reflections going towards the diode. It is a very unusual set up as lasers seem to go...I may remove it and play the odds to see what it does. The crystal does in fact lase with another lower powered diode and OC. So this eliminates a coating mishap. The pump focus optics are not in question. It is this oddity....I was just wanting to see if anyone could explain how to fields of the TE and TM field could exist if one or the other were to be deminished in capacity with out regards to the other in some small amount. Further investigation is needed for me here. The optic in question is rather thick at 4.2mm...with coatings both sides. Purple hue on one side and the Yag side has an aqua hue. I am hesitant on removing it until a valid reason for it's being there is explained. The reason behind thinking of a polorised wave plate is that tests performed earlier yielded rotation does in fact retard 808nm and 532. It could be as simple as to control the backward travelling green beam. Why from the diode and not the Yag who knows...maybe wrong assumption there as well. More tests done soon.
03-20-2009, 16:34
mixedgas

Sounds like a quarter waveplate and circular polarization to me, spoils the back reflection from killing the faucets. Also gets rid of any fabry perot effects between the vandate face and the diode.

circular polarization is best viewed by a ME type as a looking along the Z axis of a four fluted end mill , with a added rule that if you reflect it, it switches from right hand to left hand threads. Single polarization is traditionally explaned as the e field going through a picket fence. For circular, , ie the picket fence is twisted in time. Dont even get started with elliptical polarization, I draw the line at explaining that one.

google "Poincaire Sphere"

Steve
03-20-2009, 20:51
heroic

Quote:

Originally Posted by mixedgas

Single polarization is traditionally explaned as the e field going through a picket fence. For circular, , ie the picket fence is twisted in time.

For circular the picket fence is a threaded nut, right?
03-21-2009, 04:36
mixedgas

Quote:

Originally Posted by heroic

For circular the picket fence is a threaded nut, right?

well, I guess so.

Steve