Application of VCSEL in Bio-Sensing Atomic Magnetometers

Abstract

Recent years have seen rapid development of chip-scale atomic devices due to their great potential in the field of biomedical imaging, namely chip-scale atomic magnetometers that enable high resolution magnetocardiography (MCG) and magnetoencephalography (MEG). For atomic devices of this kind, vertical cavity surface emitting lasers (VCSELs) have become the most crucial components as integrated pumping sources, which are attracting growing interest. In this paper, the application of VCSELs in chip-scale atomic devices are reviewed, where VCSELs are integrated in various atomic bio-sensing devices with different operating environments. Secondly, the mode and polarization control of VCSELs in the specific applications are reviewed with their pros and cons discussed. In addition, various packaging of VCSEL based on different atomic devices in pursuit of miniaturization and precision measurement are reviewed and discussed. Finally, the VCSEL-based chip-scale atomic magnetometers utilized for cardiac and brain magnetometry are reviewed in detail. Nowadays, biosensors with chip integration, low power consumption, and high sensitivity are undergoing rapid industrialization, due to the growing market of medical instrumentation and portable health monitoring. It is promising that VCSEL-integrated chip-scale atomic biosensors as featured applications of this kind may experience extensive development in the near future.

Keywords: VCSEL; chip-scale atomic magnetometers; magnetocardiography; magnetoencephalography.

Figure 8

Anisotropic loss VCSEL (a) schematic cross-sectional layout of the VCSEL with rectangular column [64]; (b) schematic cross-sectional layout of the VCSEL with tilt column [67]; (c) schematic drawing of the VCSEL with the oxidized “T-bars” [68]; (d) SEM images of the fabricated photonic crystal VCSEL [71].

Figure 1

Structure of VCSEL.

Figure 2

(a) Structure of SERF magnetometer; (b) structure of the Bell–Bloom type SERF magnetometer.

Figure 3

(a) Structure of M-x magnetometers; (b) dispersive signal as a function of the magnetic field.

Figure 4

Structure of the different methods for realizing single-mode outputs (a) Extended cavity VCSEL; (b) ion implantation VCSEL.

Figure 5

Different structures to realize single-mode outputs (a) surface relief VCSEL; (b) photonic crystal VCSEL.

Figure 6

(a) Cross-sectional schematic of the PCSEL; (b) top-view SEM image of the 2D PC and side-view SEM image of the 2D PC [53].

Figure 7

(a) Double-sided VCSEL structure and its beam shaping effect [58]; (b) schematics of the 940 nm HCG-VCSEL [57].

Figure 9

(a) VCSEL with symmetric current injection; (b) VCSEL with asymmetric current injection.

Figure 10

The experimental setup for differential detection [91].

Figure 11

(a) The experimental setup for differential detection; (b) the lock-in signals after differential detection and of the single photo detector [102].

Figure 12

(a) Conceptual sketch of integrated magnetic sensor array; (b) schematic illustration showing the operation of spin selector; (c) scanning electron microscope(SEM) of the fabricated device [116].

Figure 13

Amplitude of various biomagnetism signals in comparison to the geofield and urban magnetic noise [123].

Figure 14

(a) Schematic set up of the optically-pumped Mx-magnetometer in the phase-locked mode; (b) MCGs taken on the grid above the chest, where P indicates atrial depolarization, QRS is responsible for ventricular depolarization, and T represents ventricular repolarization [122].

Figure 15

Position labels of the 8 × 8 array with 30 mm intervals, QZFM magnetometer and customized receptacles [127].

Figure 16

(a) Physical packaging of magnetometer; (b) magnetometer structure schematic [128].

Figure 17

(a) Physical packaging of magnetometer; (b) experimental map of the brain magnetometer [129].

Figure 18

A fiber-optically coupled chip-scale atomic magnetometer. (a) the vacuum assembly housing the vapor cell; (b) a schematic of the optical bench; (c) a photograph of the final package [8].

Figure 19

The 3D printed head model used for the experiments [130].