Anyone have any ideas on how I could improve my character jump to make it more realistic?

I would like the jump to last 0.7s from start to finish and beginning and ending of jump is slightly faster that the middle.

using System.Collections;
using UnityEngine;

public class MoveOrb : MonoBehaviour {

public KeyCode moveL;
public KeyCode moveR;
public KeyCode jump;

public float slideSpeed = 0;
public float playerSpeed = 4;
public int laneNum = 2;
public string controlLocked = "n";
public float jumpHeight = 8;
public bool isAirBorn = false;
public float vertVel = 0;

void Start () {

}

void Update () {

    //Move Character                                    X      Y       Z
    GetComponent<Rigidbody>().velocity = new Vector3(slideSpeed, vertVel, playerSpeed);

    if((Input.GetKeyDown(moveL)) && (laneNum > 1) && (controlLocked == "n")) {
        slideSpeed = -4;
        StartCoroutine(stopSlide());

        laneNum -= 1;
        controlLocked = "y";
    }
    if((Input.GetKeyDown(moveR)) && (laneNum < 3) && (controlLocked == "n")) {
        slideSpeed = 4;
        StartCoroutine(stopSlide());

        laneNum += 1;
        controlLocked = "y";
    }
    if((Input.GetKeyDown(jump)) && (isAirBorn == false)) {
        vertVel += 10;
        isAirBorn = true;
        StartCoroutine(stopJump());
    }
}

void OnCollisionEnter(Collision other) {
    if(other.gameObject.tag == "lethal") {
        Debug.Log("Object Has Hit Lethal Block");
        Destroy(gameObject);
    }
    if(other.gameObject.tag == "ground") {
        isAirBorn = false;
    }
}

void OnTriggerEnter(Collider other) {
    if(other.gameObject.name == "rampbottomTrig") {
        vertVel = 1;
    }
    if (other.gameObject.name == "ramptopTrig") {
        vertVel = 0;
    }
}

IEnumerator stopSlide() {
    yield return new WaitForSeconds(.3f);
    slideSpeed = 0;
    controlLocked = "n";
}
IEnumerator stopJump() {
    yield return new WaitForSeconds(.35f);
    vertVel = 0;
}

}

Thank you!

Have you tried using RigidBody2d.Addforce() ?
That should give you the desired momentum based jump with applied gravity.