A Fusion-Spliced Near-Field Optical Fiber Probe Using Photonic Crystal Fiber for Nanoscale Thermometry Based on Fluorescence-Lifetime Measurement of Quantum Dots

Takuro Fujii,Toshiharu Saiki,Yuji Nagasaka,Yoshihiro Taguchi

doi:10.3390/s110908358

Abstract

We have developed a novel nanoscale temperature-measurement method using fluorescence in the near-field called Fluorescence Near-field Optics Thermal Nanoscopy (Fluor-NOTN). Fluor-NOTN enables the temperature distributions of nanoscale materials to be measured in vivo/in situ. The proposed method measures temperature by detecting the temperature dependent fluorescence lifetimes of Cd/Se Quantum Dots (QDs). For a high-sensitivity temperature measurement, the auto-fluorescence generated from a fiber probe should be reduced. In order to decrease the noise, we have fabricated a novel near-field optical-fiber probe by fusion-splicing a photonic crystal fiber (PCF) and a conventional single-mode fiber (SMF). The validity of the novel fiber probe was assessed experimentally by evaluating the auto-fluorescence spectra of the PCF. Due to the decrease of auto-fluorescence, a six- to ten-fold increase of S/N in the near-field fluorescence lifetime detection was achieved with the newly fabricated fusion-spliced near-field optical fiber probe. Additionally, the near-field fluorescence lifetime of the quantum dots was successfully measured by the fabricated fusion-spliced near-field optical fiber probe at room temperature, and was estimated to be 10.0 ns.

Highlights

As highly integrated nano- and micro-scale devices have been developed over the last few decades, thermal design techniques at the nanoscale have become quite important
We propose a novel low-auto-fluorescence fiber probe that is fabricated by fusion-splicing a Photonic Crystal Fiber (PCF) and a conventional Single Mode Fiber (SMF)
We have proposed a novel nano-scale thermometry method based on the near-field fluorescence-lifetime measurement of Quantum Dots (QDs)

Summary

Introduction

As highly integrated nano- and micro-scale devices have been developed over the last few decades, thermal design techniques at the nanoscale have become quite important. Scanning Thermal Microscopy (SThM) method using a thermocouple probe tip can achieve nanoscale spatial resolution; the heat transfer mechanism between the probe and the sample is still unverified [1,2]. Another contact-mode device, the Ga-filled carbon nano-thermometer, has the capability of measuring temperatures from room temperature to approximately 1,000 °C at the nano-scale [3,4]. Generally in contact-mode methods, there is a concern that nano-structured samples may suffer damage due to the friction between the sample and the probe; the temperature change due to heat transfer during the operation can be significant

Methods

Results

Conclusion