Consiglio Nazionale Delle Ricerche

Antonio Giorgini

Paolo De Natale

Gianluca Gagliardi

Saverio Avino

Pietro Malara

A method to measure the refractive index of a sample, includes: providing a plasmonic sensor including a sensing surface in contact with the sample; providing an optical resonator, the plasmonic sensor being integrated therein as a reflecting surface; providing a first input field of electromagnetic radiation as a primary carrier; providing a second input field of electromagnetic radiation as a secondary carrier having a second frequency different from the first and defined as: second frequency=first frequency+&#x394;v and having a TE and/or a TM polarized component; impinging simultaneously with the first and second input field the plasmonic sensor; tuning the frequency of the first field and/or the value of &#x394;v; detecting a resonator output power corresponding to the first and second intra-cavity fields resonating; determining a difference between the first and the second resonating frequencies; and calculating the refractive index of the sample from the difference.

Method to measure the refractive index of a sample using surface plasmon polaritons

The present invention relates to a method and an apparatus to perform frequency comb spectroscopy. The method includes: &#x2014;Arranging a waveguide optical cavity () having a plurality of cavity mode frequencies with a cavity mode frequency spacing (FSR), said waveguide optical cavity being dispersive so that the frequency spacing of the cavity modes is wavelength dependent; &#x2014;Arranging a sample (S) with respect to the waveguide optical cavity () so that the sample is capable of absorbing light travelling into the waveguide optical cavity; &#x2014;Coupling pulsed light coming from a light source () into the waveguide optical cavity (), the source light including source comb frequencies (OCF) with a source frequency spacing (RR), the coupled light including an interval of frequencies centered on a main frequency of said comb frequencies due to cavity dispersion; &#x2014;Locking the waveguide optical cavity to the frequency comb at said main optical frequency; &#x2014;Detecting transmitted cavity frequencies; &#x2014;Determining absorption by said sample (S) of said main optical frequency from the detected transmitted frequencies, &#x2014;Changing the cavity mode frequency (FSR) spacing or the source frequency spacing (RR); &#x2014;Coupling the pulse light to the waveguide optical cavity (), the coupled light including an interval of frequencies centered on a second main frequency of said comb frequencies due to cavity dispersion; &#x2014;Locking the waveguide optical cavity to the frequency comb at said second main optical frequency; &#x2014;Detecting transmitted cavity frequencies; &#x2014;Determining absorption by said sample of said second main optical frequency from the detected transmitted frequencies.

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Florence, Italy

Antonio Giorgini