The overall goal of this procedure is to create a reference interferometer that uses Whispering Gallery mode sensing to detect particles with diameters on the order of tens of nanometers for an ultra high quality factor. Whispering gallery mode, micro cavity and resonance photon circulate within it hundreds of thousands of times. This will cause optical properties to noticeably change when a particle lands on the micro cavity.
If back scattering is sufficiently strong and cavity loss is sufficiently low, a para split modes appear experimentally. This will produce the effect of frequency splitting and particle absorption occurs. Frequency shifting will then take place.
The main advantage of this referencing interferometer technique over the existing system, such as those tracking the resonance frequency of cavity through looking at the scanning voltage, is that this is capable of for suppress the laser noise and therefore boost the signal by all of magnitude. Now, besides this is easy to construct and cost effective, This method is particularly suited for studying or exploiting the properties of a wide range of area motor captive and for the rib detection of single molecules like influenza, a virus. To begin assembling the reference interferometer direct a 600 to 800 nanometer single mode optical fiber towards the input of a three DB directional coupler.
One of the output fibers of this coupler should form a 16 foot long series of loops as to add optical delay. The remaining output fiber should be clamped to a polarization controller, which will be later used to tune optical transmission. After connecting these fibers to the input ports of a second three DB directional coupler, the photo mixed output signals will then serve as inputs for a balanced photo detector.
This network of optical components can be housed on a three stage shelving unit, which lies in a styrofoam box enclosed acrylic basin to be filled with 50%ice mixed with 50%liquid water shaved ice is preferred over ice cubes for stability purposes. Yet both must be carefully placed in the enclosure as to avoid damaging optical fibers. It is then possible to incorporate this within an existing configuration capable of probing a whispering gallery mode micro cavity.
First, ensure that the probe blazer output is received at the initial three DB directional coupler to linearly scan the laser feed a 100 herz one volt peak to peak ramp signal. The output of the balance photo detector should then become sinusoidal. The next step is to appropriately tune the polarization controller as to optimize the peak tope voltage of the sinusoidal waveform.
To configure the laser for continuous wave output, set the waveform generator to DC mode and tune it so that the previous signal fluctuates around zero. By monitoring the signal with an electrical spectrum analyzer, the free spectral range can finally be determined. This can be accomplished by finding the frequency separation between the maximum at zero frequency and the first null.
Fix the fiber holder to the motorized translation stage. After adding FC A PC connectors to one end of two optical fibers, remove the buffer coating from the exposed ends with a fiber stripper. Clean these with acetone followed by isopropanol.
Then lea the end facets. Be sure to safely dispose of the excess fiber. The next step is diffusion.
Splice these fibers together Upon splicing. Clamp the right and left boundaries of the new fiber segment to a fiber holder so that it is near a hydrogen gas outlet and can be seen through an optical microscope objective. When hydrogen gas is released, the channel pressure stabilizes and the flow rate becomes 110 milliliters per minute.
Ignite the hydrogen while monitoring the optical transmission by viewing the photo detector signal on an oscilloscope linearly. Pull the fiber using custom lab use software. You should notice the fiber width gradually decreasing and that the transmitted intensity should begin to oscillate due to multimode interference.
Once the transmitted intensity ceases to vary, stop pulling the fiber. This marks the point where the taper thin enough to support a single cladding mode. Release the fiber holder from the translation stage and secure it near the PAs and electric stage that will support your micro cavity.
During this part of the procedure, a clean room suit must be worn to avoid contaminating the samples with foreign particles. This includes shoe covers, A face mask, protective eyewear, a hairnet, and a pair of latex gloves. After setting up your workstation, fetch the 50 nanometer radius mono disperse holy starring microspheres, which should have been stored at four degrees Celsius when not in use.
Once a 10 picomolar solution of microspheres in ECCOs phosphate buffered saline or DPBS has been prepared, create a pure DPBS solution in a one milliliter centrifuge tube using a micropipet. Next, inject 900 microliters of DPBS into two more tubes. Keep in mind that separate pipette tips should be used for different mixtures.
To prepare the diluted one pico molar and 100 femto molar solutions of microspheres in DPBS extract 100 microliters from your original 10 pico molar solution and dispense this in one of the tubes containing 900 microliters of DPBS. Briefly vortex, mix the contents, then remove 100 microliters from the one pico molar solution and repeat the previous step for the remaining two. Afterwards, open the lids of the centrifuge.
Place the solutions within it, ensuring that the positions are staggered for balance purposes. Close the lids And initiate a 30 minute spinning cycle Upon completion, Open the lids and carefully remove the solutions. Secure the tubes within a desiccate chamber.
Lightly unscrew their caps and evacuate the chamber to Degas the mixtures, partially submerge the desiccate in the bath of a sonicate and bombard the solutions with ultrasound waves for 30 minutes. Following this, remove the chamber from the bath. Remove, remove, remove, refill it with air and collect the solutions.
Remember to screw the caps closed on the centrifuge tubes. The next steps will focus on constructing a fluid delivery system. Once a stand has been built, cut a segment of microfluidic tubule that is slightly longer than one foot.
Insert a syringe tip onto one end and connect it to the lur lock fitting of a barrel plunder assembly. Then screw two syringe tips to both ends of a feral. Insert one of these syringe tips to the exposed end of the microfluidic tubule and fix it to the stand prop.
The microfluidic system directly behind the sample has to minimize spillage. Refocus the vertical microscope objective in order to acquire a sharp image of the fiber taper. Repeat this for the horizontal microscope objective.
You may then mount your sample on the nano positioner and displace it towards the center of the fiber taper. In this case, O silica microsphere is used. Next, scan the laser wavelength as to obtain an appropriate resonance dip on the oscilloscope.
Once you have assessed the quality factor of the micro cavity, carefully move its fiber taper away from the structure. If the fiber taper is close enough to the micro cavity, Vander Wall's forces will attract them together so that they contact one another. This will likely produce over coupling, which you can correct by separating the structures Once more, load a pastel pipette with water and add drops behind the micro cavity so that its surrounding dielectric medium becomes this liquid.
You are now ready to flow solutions to the sample. Now that the reference interferometry system is set up, configure the oscilloscope trigger settings and run homemade software to collect traces. You may then acquire resonance curves for the buffer solution, which should at most exhibit frequency splitting next record, resus curves for the nanoparticle solutions from lowest to highest concentration.
Here you should expect to see average and split frequency shifts that correspond to binding events. The trace data can be processed with the aid of MATLAB scripts and this particular example, the quality factor can be retrieved by comparing the resonance structure in the upper sub plot to the interferometer signal. In the bottom sub plot, the quality factor of this particular run is around 200 million for immersion in the buffer solution.
Furthermore, spectrograms prior to calibration, spectrograms post calibration and noise floor wave forms can be generated After constructing the referenceing informers through this procedure. By now, you should have a good understanding how this work variety of resident assistance and how to couple them into your own system. Besides, you should have a good understanding to how to accomplish self-reference detections through the whispering error mode cavities.
