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Re: SHG

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Eli Rothenberg

Re: SHG

Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

Hi Sarah,

If you double the frequency of your laser
and get a wavelength that is resonant to your fluorophore's absorption then it is a regular one-photon excitation and
you get linear dependence between your doubled laser and
emission intensity.

You have to make sure you carefully filter the remaining of the Ti:Sa laser after doubling, so you won't have 2P events
as well.

If the doubling crystal is your own "home built" addition, you don't place it in the Ti:Sa cavity but rather after it.
I guess you're using a BBO or LBO, in which case a 5mm by 5mm
piece will be enough, coming to it at a tight focus.
Finding the "mismatch" axis and aligning it is a bit tricky and requires 6 degrees of freedom (x-y-z rotational and angular).

Hope this helped- good luck,

Eli

6 degreess

---- Original message ----

>Date: Thu, 8 May 2008 09:34:58 +0800
>From: Peng Xi <[hidden email]>
>Subject: Re: SHG
>To: [hidden email]
>
>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Hi Sarah,
> Just like you asked, it will be an one-photon excitation. So,
>although it is possible that you create a femtosecond 400nm laser pulse,
>it is still linear excitation -- one photon process. Thank you!
> I am very interested in the experiment itself -- have you tried to
>put a SHG crystal inside the Ti:Sa laser cavity and see the 400nm emission?
>
>Best regards,
>Peng Xi
>Associate Professor
>Institute for Laser Medicine and Biophotonics
>Shanghai Jiao Tong University
>800 Dongchuan Rd.
>Shanghai 200240, China
>Tel: (86) 21-3420-4076
>http://biophotonics.sjtu.edu.cn/
>
>
>
>Sarah Kefayati wrote:
>> Search the CONFOCAL archive at
>> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>> Hello all,
>>
>> I appreciate if you could help me with my question:
>>
>> I just want to make sure about this fact that by using a non-linear
>> crystal in the path of my Ti-sapphire laser I will have the frequency
>> doubled beam which excites my sample via traditional one-photon
>> excitation.
>> But dose the intensity of the emitted fluorescence depend on
>> excitation power linearly or quadratically?
>>
>> any information in this regard is highly appreciated.
>>
>> Thanks
>> Sarah

________________________________
Eli Rothenberg, Ph.D.
Post Doctoral Research Associate,
Howard Hughes Medical Institute,
Department of Physics,
University of Illinois,
Urbana-Champaign. 61801.
Illinois, USA
Tel: +217-333-3393;
Fax: +217-244-7187;
Email: [hidden email]

Craig Brideau

Re: SHG

Search the CONFOCAL archive at http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal I've interspersed a few of my own comments below:

You have to make sure you carefully filter the remaining of the Ti:Sa laser after doubling, so you won't have 2P events
as well.

Typically a good short pass filter centered at 600 or 650 will do the job. Keep it at right-angles to the beam.

If the doubling crystal is your own "home built" addition, you don't place it in the Ti:Sa cavity but rather after it.

Yeah, a doubling crystal in the cavity will potentially wreck the laser if it's not built for it.

I guess you're using a BBO or LBO, in which case a 5mm by 5mm
piece will be enough, coming to it at a tight focus.

Typically you get a very thin slip of crystal, almost like a microscope cover slip. Normally this comes mounted in a 1" metal circle or some 'frame' that you can place in an optical mount.

Finding the "mismatch" axis and aligning it is a bit tricky and requires 6 degrees of freedom (x-y-z rotational and angular).

If you have a 1/2 waveplate to rotate the polarization of your laser it takes one degree of freedom out of the equation (or that is to say transfers it to the waveplate, which is simple to rotate). In the case of the waveplate you want to rotate it around the optical axis. That is to say pretend your laser beam is an axle and the waveplate is a wheel rotating around it. Adjust the polarization of your laser beam such that it is perpendicular to the table surface. If you are very lucky your laser might already be this way naturally. This means you might be able to get away without the waveplate. The crystal, on the other hand, you want to first align so that it's preferred polarization is the same as the laser, i.e. perpendicular to the table if that's the laser's polarization (or you made it that way with the waveplate). Usually there's a mark for this on the crystal mount/frame. You then want to turn the crystal on an axis which is also perpendicular to the table. Thorlabs and Newport both carry appropriate mounts for doing this sort of thing. Again, the crystal manufacturers, or even the technical support guys at Thor or Newport, can generally help you out. Once you get SHG just gently play with all the degrees of freedom until you get a maximum. Measure the power after the short pass filter and seek the highest value.

Craig

Hope this helped- good luck,

Eli

6 degreess

---- Original message ----
>Date: Thu, 8 May 2008 09:34:58 +0800
>From: Peng Xi <[hidden email]>
>Subject: Re: SHG
>To: [hidden email]
>
>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Hi Sarah,
> Just like you asked, it will be an one-photon excitation. So,
>although it is possible that you create a femtosecond 400nm laser pulse,
>it is still linear excitation -- one photon process. Thank you!
> I am very interested in the experiment itself -- have you tried to
>put a SHG crystal inside the Ti:Sa laser cavity and see the 400nm emission?
>
>Best regards,
>Peng Xi
>Associate Professor
>Institute for Laser Medicine and Biophotonics
>Shanghai Jiao Tong University
>800 Dongchuan Rd.
>Shanghai 200240, China
>Tel: (86) 21-3420-4076
>http://biophotonics.sjtu.edu.cn/
>
>
>
>Sarah Kefayati wrote:
>> Search the CONFOCAL archive at
>> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>> Hello all,
>>
>> I appreciate if you could help me with my question:
>>
>> I just want to make sure about this fact that by using a non-linear
>> crystal in the path of my Ti-sapphire laser I will have the frequency
>> doubled beam which excites my sample via traditional one-photon
>> excitation.
>> But dose the intensity of the emitted fluorescence depend on
>> excitation power linearly or quadratically?
>>
>> any information in this regard is highly appreciated.
>>
>> Thanks
>> Sarah

________________________________
Eli Rothenberg, Ph.D.
Post Doctoral Research Associate,
Howard Hughes Medical Institute,
Department of Physics,
University of Illinois,
Urbana-Champaign. 61801.
Illinois, USA
Tel: +217-333-3393;
Fax: +217-244-7187;
Email: [hidden email]

Sarah Kefayati

Re: SHG

Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

Dear Craig,

Thank you very much for the information.

I aligned the crystal and I got the blue beam and I block the 2p with
the filter.I didn't use any polarizer in the path.is it possible that
I am not getting the highest value and I should use the polarizer or
once I get the blue it means that my laser beam is polarized in the
same way of the crystal and I don't need to try waveplate?

Thanks
Sarah

On Thu, May 8, 2008 at 1:10 AM, Craig Brideau <[hidden email]> wrote:

> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal I've interspersed a
> few of my own comments below:
>
> >
> > You have to make sure you carefully filter the remaining of the Ti:Sa
> laser after doubling, so you won't have 2P events
> > as well.
>
> Typically a good short pass filter centered at 600 or 650 will do the job.
> Keep it at right-angles to the beam.
>
> >
> > If the doubling crystal is your own "home built" addition, you don't place
> it in the Ti:Sa cavity but rather after it.
> >
>
> Yeah, a doubling crystal in the cavity will potentially wreck the laser if
> it's not built for it.
>
> > I guess you're using a BBO or LBO, in which case a 5mm by 5mm
> > piece will be enough, coming to it at a tight focus.
>
> Typically you get a very thin slip of crystal, almost like a microscope
> cover slip. Normally this comes mounted in a 1" metal circle or some
> 'frame' that you can place in an optical mount.
>
> >
> > Finding the "mismatch" axis and aligning it is a bit tricky and requires 6
> degrees of freedom (x-y-z rotational and angular).
>
> If you have a 1/2 waveplate to rotate the polarization of your laser it
> takes one degree of freedom out of the equation (or that is to say transfers
> it to the waveplate, which is simple to rotate). In the case of the
> waveplate you want to rotate it around the optical axis. That is to say
> pretend your laser beam is an axle and the waveplate is a wheel rotating
> around it. Adjust the polarization of your laser beam such that it is
> perpendicular to the table surface. If you are very lucky your laser might
> already be this way naturally. This means you might be able to get away
> without the waveplate. The crystal, on the other hand, you want to first
> align so that it's preferred polarization is the same as the laser, i.e.
> perpendicular to the table if that's the laser's polarization (or you made
> it that way with the waveplate). Usually there's a mark for this on the
> crystal mount/frame. You then want to turn the crystal on an axis which is
> also perpendicular to the table. Thorlabs and Newport both carry
> appropriate mounts for doing this sort of thing. Again, the crystal
> manufacturers, or even the technical support guys at Thor or Newport, can
> generally help you out. Once you get SHG just gently play with all the
> degrees of freedom until you get a maximum. Measure the power after the
> short pass filter and seek the highest value.
>
> Craig
>
>
>
> >
> >
> >
> > Hope this helped- good luck,
> >
> > Eli
> >
> >
> > 6 degreess
> >
> >
> >
> >
> >
> > ---- Original message ----
> > >Date: Thu, 8 May 2008 09:34:58 +0800
> > >From: Peng Xi <[hidden email]>
> > >Subject: Re: SHG
> > >To: [hidden email]
> > >
> > >Search the CONFOCAL archive at
> > >http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
> > >
> > >Hi Sarah,
> > > Just like you asked, it will be an one-photon excitation. So,
> > >although it is possible that you create a femtosecond 400nm laser pulse,
> > >it is still linear excitation -- one photon process. Thank you!
> > > I am very interested in the experiment itself -- have you tried to
> > >put a SHG crystal inside the Ti:Sa laser cavity and see the 400nm
> emission?
> > >
> > >Best regards,
> > >Peng Xi
> > >Associate Professor
> > >Institute for Laser Medicine and Biophotonics
> > >Shanghai Jiao Tong University
> > >800 Dongchuan Rd.
> > >Shanghai 200240, China
> > >Tel: (86) 21-3420-4076
> > >http://biophotonics.sjtu.edu.cn/
> > >
> > >
> > >
> > >Sarah Kefayati wrote:
> > >> Search the CONFOCAL archive at
> > >> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
> > >> Hello all,
> > >>
> > >> I appreciate if you could help me with my question:
> > >>
> > >> I just want to make sure about this fact that by using a non-linear
> > >> crystal in the path of my Ti-sapphire laser I will have the frequency
> > >> doubled beam which excites my sample via traditional one-photon
> > >> excitation.
> > >> But dose the intensity of the emitted fluorescence depend on
> > >> excitation power linearly or quadratically?
> > >>
> > >> any information in this regard is highly appreciated.
> > >>
> > >> Thanks
> > >> Sarah
> > ________________________________
> > Eli Rothenberg, Ph.D.
> > Post Doctoral Research Associate,
> > Howard Hughes Medical Institute,
> > Department of Physics,
> > University of Illinois,
> > Urbana-Champaign. 61801.
> > Illinois, USA
> > Tel: +217-333-3393;
> > Fax: +217-244-7187;
> > Email: [hidden email]
> >
>
>

Peng Xi-2

Re: SHG

Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

I remember that BBO crystal has a certain acceptance angle, which means
that generating the blue doesn't necessarily mean optimized polarization
angle. You should try rotating the crystal to find the maximum
upconversion.

Cheers,
Peng
Institute for Laser Medicine and Biophotonics
Shanghai Jiao Tong University
800 Dongchuan Rd.
Shanghai 200240, China
Tel: (86) 21-3420-4076
http://biophotonics.sjtu.edu.cn/

Sarah Kefayati wrote:

Elijah-15

Re: SHG

In reply to this post by Sarah Kefayati

Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

Dear Sarah,

Not necessarily. Best to confirm with a polarizer that you're getting out
the same as what you put in. As far as I know it is possible to get out a
different polarization (Type I or Type II SHG).

Elijah

----- Original Message -----
From: "Sarah Kefayati" <[hidden email]>
To: <[hidden email]>
Sent: Thursday, May 08, 2008 1:46 PM
Subject: Re: SHG

> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Dear Craig,
>
> Thank you very much for the information.
>
> I aligned the crystal and I got the blue beam and I block the 2p with
> the filter.I didn't use any polarizer in the path.is it possible that
> I am not getting the highest value and I should use the polarizer or
> once I get the blue it means that my laser beam is polarized in the
> same way of the crystal and I don't need to try waveplate?
>
> Thanks
> Sarah
>
> On Thu, May 8, 2008 at 1:10 AM, Craig Brideau <[hidden email]>
> wrote:
>> Search the CONFOCAL archive at
>> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal I've interspersed
>> a
>> few of my own comments below:
>>
>> >
>> > You have to make sure you carefully filter the remaining of the Ti:Sa
>> laser after doubling, so you won't have 2P events
>> > as well.
>>
>> Typically a good short pass filter centered at 600 or 650 will do the
>> job.
>> Keep it at right-angles to the beam.
>>
>> >
>> > If the doubling crystal is your own "home built" addition, you don't
>> > place
>> it in the Ti:Sa cavity but rather after it.
>> >
>>
>> Yeah, a doubling crystal in the cavity will potentially wreck the laser
>> if
>> it's not built for it.
>>
>> > I guess you're using a BBO or LBO, in which case a 5mm by 5mm
>> > piece will be enough, coming to it at a tight focus.
>>
>> Typically you get a very thin slip of crystal, almost like a microscope
>> cover slip. Normally this comes mounted in a 1" metal circle or some
>> 'frame' that you can place in an optical mount.
>>
>> >
>> > Finding the "mismatch" axis and aligning it is a bit tricky and
>> > requires 6
>> degrees of freedom (x-y-z rotational and angular).
>>
>> If you have a 1/2 waveplate to rotate the polarization of your laser it
>> takes one degree of freedom out of the equation (or that is to say
>> transfers
>> it to the waveplate, which is simple to rotate). In the case of the
>> waveplate you want to rotate it around the optical axis. That is to say
>> pretend your laser beam is an axle and the waveplate is a wheel rotating
>> around it. Adjust the polarization of your laser beam such that it is
>> perpendicular to the table surface. If you are very lucky your laser
>> might
>> already be this way naturally. This means you might be able to get away
>> without the waveplate. The crystal, on the other hand, you want to first
>> align so that it's preferred polarization is the same as the laser, i.e.
>> perpendicular to the table if that's the laser's polarization (or you
>> made
>> it that way with the waveplate). Usually there's a mark for this on the
>> crystal mount/frame. You then want to turn the crystal on an axis which
>> is
>> also perpendicular to the table. Thorlabs and Newport both carry
>> appropriate mounts for doing this sort of thing. Again, the crystal
>> manufacturers, or even the technical support guys at Thor or Newport, can
>> generally help you out. Once you get SHG just gently play with all the
>> degrees of freedom until you get a maximum. Measure the power after the
>> short pass filter and seek the highest value.
>>
>> Craig
>>
>>
>>
>> >
>> >
>> >
>> > Hope this helped- good luck,
>> >
>> > Eli
>> >
>> >
>> > 6 degreess
>> >
>> >
>> >
>> >
>> >
>> > ---- Original message ----
>> > >Date: Thu, 8 May 2008 09:34:58 +0800
>> > >From: Peng Xi <[hidden email]>
>> > >Subject: Re: SHG
>> > >To: [hidden email]
>> > >
>> > >Search the CONFOCAL archive at
>> > >http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>> > >
>> > >Hi Sarah,
>> > > Just like you asked, it will be an one-photon excitation. So,
>> > >although it is possible that you create a femtosecond 400nm laser
>> > >pulse,
>> > >it is still linear excitation -- one photon process. Thank you!
>> > > I am very interested in the experiment itself -- have you tried to
>> > >put a SHG crystal inside the Ti:Sa laser cavity and see the 400nm
>> emission?
>> > >
>> > >Best regards,
>> > >Peng Xi
>> > >Associate Professor
>> > >Institute for Laser Medicine and Biophotonics
>> > >Shanghai Jiao Tong University
>> > >800 Dongchuan Rd.
>> > >Shanghai 200240, China
>> > >Tel: (86) 21-3420-4076
>> > >http://biophotonics.sjtu.edu.cn/
>> > >
>> > >
>> > >
>> > >Sarah Kefayati wrote:
>> > >> Search the CONFOCAL archive at
>> > >> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>> > >> Hello all,
>> > >>
>> > >> I appreciate if you could help me with my question:
>> > >>
>> > >> I just want to make sure about this fact that by using a non-linear
>> > >> crystal in the path of my Ti-sapphire laser I will have the
>> > >> frequency
>> > >> doubled beam which excites my sample via traditional one-photon
>> > >> excitation.
>> > >> But dose the intensity of the emitted fluorescence depend on
>> > >> excitation power linearly or quadratically?
>> > >>
>> > >> any information in this regard is highly appreciated.
>> > >>
>> > >> Thanks
>> > >> Sarah
>> > ________________________________
>> > Eli Rothenberg, Ph.D.
>> > Post Doctoral Research Associate,
>> > Howard Hughes Medical Institute,
>> > Department of Physics,
>> > University of Illinois,
>> > Urbana-Champaign. 61801.
>> > Illinois, USA
>> > Tel: +217-333-3393;
>> > Fax: +217-244-7187;
>> > Email: [hidden email]
>> >
>>
>>

Craig Brideau

Re: SHG

In reply to this post by Sarah Kefayati

Search the CONFOCAL archive at http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

I aligned the crystal and I got the blue beam and I block the 2p with
the filter.

Congratulations! Welcome to the world of non-linear optics. @:-)

I didn't use any polarizer in the path.is it possible that
I am not getting the highest value and I should use the polarizer or
once I get the blue it means that my laser beam is polarized in the
same way of the crystal and I don't need to try waveplate?

Your laser's polarization is probably close enough to perpendicular that it won't matter. If you have enough blue light power for your purposes then you can probably get away without the waveplate. If it still seems low then try a waveplate, although they are expensive. Typical conversion efficiencies for these crystals range from 20-40%. If you are close to 20% or better then I wouldn't bother with the waveplate unless you don't have enough blue light for what you want to do.

Good luck!

Craig